"Lifetime" in electronics is 5 years Max.

So, yes, replace it.

This is PCM - Phase Change Material.
When it stops being soft when heated, that's when it needs to be replaced.
But it's impossible to determine when that moment will come, so it needs to be replaced every ~5 years.

And after that, you need to be very careful with the microchip crystals.
Because PCM was developed precisely to prevent radiator displacement in a transport (cold) state.

ah no worries, this has sturdy springs to keep it attached.
This would still get soft BTW. The thermal paste was desert sand though. The machine is from 2008.

Thanks for the feedback!

My prefered method for removing a heatsink that uses this stuff is to run the computer to get it warmed up, sometimes even with the fan disconnected, so that it becomes pliable and easier to pull the heatsink. After that I scrape away at it, little by little, with toothpicks picking off the clumps as I go. Once there is only a thin residue left behind tradditional methods of cleaning up heatsink compounds work just fine.

indeed - I use 100C hot air on the heatsink, it comes off in 30 seconds. Then I keep warming up the stuff and remove it with cotton buds and or their stems.

(PS: First time I didn't know, took me forever!)