Turning it on and off won't hurt the filament. What generally degrades CRTs (beside obvious user errors) are:
1) poor quality components (capacitors are usual suspect when monitor fails).
2) leaving it on showing the same picture for prolonged periods of time (it will 'burn' the image into the luminophore.
3) setting the brightness too high will degrade the luminophore as well.
4) temperature - partially corresponding with point 1 as it will kill the poor quality components faster.

Putting a fan inside the chassis may be a good idea if there are some areas which get very hot on the PCB (you can take a look if you see any darker spots on the board) but ViewSonic monitors are/were usually well designed and it may not really give you any advantage. I wouldn't also put any sort of heavy duty fan inside - not only because of noise, but also it will certainly make the inside more dusty drawing the dust from the outside.

I would definitely advise agains not turning off the monitor. First, it won't help anything. Filament power is shut down in the digitally controlled monitors once the video signal is gone anyway. Also keep in mind that CRTs (especially recent ones like this 15GA) are plenty and readly available for cheap. Yet we have only one Earth and it's environment. You should save the energy to limit CO2 emissions any way you can.

HanJammer wrote on 2021-09-12, 22:42:

Turning it on and off won't hurt the filament. What generally degrades CRTs (beside obvious user errors) are: 1) poor quality co […]
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Turning it on and off won't hurt the filament. What generally degrades CRTs (beside obvious user errors) are:
1) poor quality components (capacitors are usual suspect when monitor fails).
2) leaving it on showing the same picture for prolonged periods of time (it will 'burn' the image into the luminophore.
3) setting the brightness too high will degrade the luminophore as well.
4) temperature - partially corresponding with point 1 as it will kill the poor quality components faster.

Putting a fan inside the chassis may be a good idea if there are some areas which get very hot on the PCB (you can take a look if you see any darker spots on the board) but ViewSonic monitors are/were usually well designed and it may not really give you any advantage. I wouldn't also put any sort of heavy duty fan inside - not only because of noise, but also it will certainly make the inside more dusty drawing the dust from the outside.

I would definitely advise agains not turning off the monitor. First, it won't help anything. Filament power is shut down in the digitally controlled monitors once the video signal is gone anyway. Also keep in mind that CRTs (especially recent ones like this 15GA) are plenty and readly available for cheap. Yet we have only one Earth and it's environment. You should save the energy to limit CO2 emissions any way you can.

Thank you! I was also wondering if manually adjusting the brightness/contrast settings in the monitor menu turns down the voltage to the filament.

While filament definitely prefers to stay at the same temperature all the time instead of being turned on and off all over again I never seen a single CRT monitor failing due to the filament getting open. It was always due to the electronics failure (caps and flyback transformer failures were most frequent). In some rare cases I've seen badly worn CRTs with the image looking like a soap (washed out colors, and out of focus image but again it could probably be electronics issue in some beam focusing circuit).

Generally brightness of the CRT will deteriorate over time both - due to the phosphorous/luminophore deterioration and due to the filament deterioration. With the first you can't do anything. With the latter - you can increase the filament voltage usually on the PCB of the monitor (in general it's around 6 volts out of the factory but the filament will take up to 11 volts before it burns out) although It's a rather 'last resort' option and will shorten the life of such CRT for sure. Also if the brightness is not bad to begin with I would just set it reasonably low to protect the luminophore (and your health at the same time) and it won't get any worse soon (unless you are using the monitor in the scenario where it's turned on and displays image for many hours daily).

Also keep in mind that by the brightness controls of the CRT have nothing to do with how hot the filament is glowing - you are not changing it's voltage - instead you are changing the potential between the cathode and the control grid. Cathode heater (filament) voltage is set at the constant value.

HanJammer wrote on 2021-09-13, 00:09:

While filament definitely prefers to stay at the same temperature all the time instead of being turned on and off all over again I never seen a single CRT monitor failing due to the filament getting open.

I have definitely seen the trace to the filament bubble and fail full open, usually on large (20”+) Viewsonics, had to jumper wire point to point from the supply to the filament.
When I asked my signals and circuits engineering lab teacher he thought it looked like heat damage.

That would make me think shutting things down or even unplugging isn’t a bad idea.

I would imagine that dusting them out with an air duster from time to time would help reduce chances of high voltage flashover that will kill the coil and maybe other components quicker.

Edit: my other tip is to get a monitor that you hate but "can't replace" while it still works, so no excuse to buy a decent one. Any that I had like that, that you wished were a little sharper, or only did the resolution below the one you wanted, were 2 inches too small or crap like that, they LIVE FOR MANY YEARS... even if you use xvidtune on Xfree86 to push the res to max at barely off the squeal. 🤣

BitWrangler wrote on 2021-09-13, 03:13:

I would imagine that dusting them out with an air duster from time to time would help reduce chances of high voltage flashover that will kill the coil and maybe other components quicker.

Edit: my other tip is to get a monitor that you hate but "can't replace" while it still works, so no excuse to buy a decent one. Any that I had like that, that you wished were a little sharper, or only did the resolution below the one you wanted, were 2 inches too small or crap like that, they LIVE FOR MANY YEARS... even if you use xvidtune on Xfree86 to push the res to max at barely off the squeal. 🤣

This one is only 640x480 so it already fits in that category. Its absolutely beautiful though, although its the only good CRT I have. My WinXP era compaq, which is a low hour tube, is horizontally collapsed. Not skilled enough with a circuit board to fix it sadly. If I were I would do it as that tube is in really really good shape.

rmay635703 wrote on 2021-09-13, 03:01:

I have definitely seen the trace to the filament bubble and fail full open, usually on large (20”+) Viewsonics, had to jumper wire point to point from the supply to the filament.
When I asked my signals and circuits engineering lab teacher he thought it looked like heat damage.

That would make me think shutting things down or even unplugging isn’t a bad idea.

The issue you described definitely seems like a design flaw to me (too thin trace used to supply power to the filament). But to be hones FORTUNATELLY I never had any experiences with 20"+ CRTs (I belive 19" was the largest I ever worked on) - I still have back pains because my first job didn't provided me with the tools (like basic cart) to move around the 17" Samsung CRTs walking the stairs up to 8 floors. With 20" or more It would surely end up with a wheelchair ;] It was such a huge relief when we replaced all of them with 15-17" Belinea LCDs which I could move 4 at once... in boxes... and it was still lighter than a single CRT 🤣.

BitWrangler wrote on 2021-09-13, 03:13:

I would imagine that dusting them out with an air duster from time to time would help reduce chances of high voltage flashover that will kill the coil and maybe other components quicker.

Edit: my other tip is to get a monitor that you hate but "can't replace" while it still works, so no excuse to buy a decent one. Any that I had like that, that you wished were a little sharper, or only did the resolution below the one you wanted, were 2 inches too small or crap like that, they LIVE FOR MANY YEARS... even if you use xvidtune on Xfree86 to push the res to max at barely off the squeal. 🤣

Yeah, that's a good tip... Also - I agree CRTs have some charm to them and I do have a (too big) collections of various CRT monitors - is it really such a bad experience to use vintage computers with a decent LCD? It's more ergonomic, takes less space, uses less power... and there are plenty of GREAT LCDs which will work beautifully with old VGAs/SVGAs readly available (Dell FP2007, hp 2035 to name a few) - they also come with Composite and S-Video inputs so they are great for older consoles and 8bit machines as well... And they are just as useful with a modern hardware as well. Honestly I find it hard to justify using a CRT nowadays (not to mention I hated CRTs to start).

Thorad wrote on 2021-09-13, 03:22:

This one is only 640x480 so it already fits in that category. Its absolutely beautiful though, although its the only good CRT I have. My WinXP era compaq, which is a low hour tube, is horizontally collapsed. Not skilled enough with a circuit board to fix it sadly. If I were I would do it as that tube is in really really good shape.

15GA is not 640x480 only. It will handle up to 1280x1024.

And about Compaq - If it's collapsed horizontally it's likely one or more caps failed - perhaps just a visual inspection will be enough to find the problem. Fix may be as easy as replacing a single cap.

Be aware that the filament is only turned off while standby on relatively modern CRTs, near the very end of the CRT era (e.g. mid 1990s+).
For almost all older ones, thus it is advisable not to have it turned on when not used.
(Edit: Power cycling too often is also a problem with many older CRTs. Observe the filament while turning it on cold. Older ones usually get very bright for a moment until the temperature causes the filaments' resistance to increase and reduce the current. This is very stressing and the majority of filament breaks occur at turn-on. More modern monitors increase the filament voltage/current slowly to avoid this stress moment, you see this by it getting brighter gradually and not "flashing up" instantly)

Horizontally collapsed image usually is caused by a problem in the vertical stage, most likely defective vertical driver, coil and connectors. Not a big issue for experienced TV repairpeople.

Extra cooling and not operating with excessive brightness is always advisable, in particular with the very last Sony's in 16:9 format, whose horizontal transformer is particularly sensitive (because undersized) and no replacement spares available.
Overly high contrast itself does not increase radiation, as the thing that causes radiation is the HV current.
But excessive focus voltage tends to wear out the tube itself prematurely, particularly a problem on Trinitrons.