The Read/Write endurance of flash memory is per block (technically per cell, but flash doesn't normally address individual cells). This endurance in turn depends on the type of cell being used. SLC NAND (1 bit per cell) has a typical write endurance of 100k writes, MLC (2 bit per cell) has between 1k and 3k for consumer memory and between 5k and 10k for enterprise memory and TLC (3 bits per cell) has only about 1k. These numbers are average numbers not guaranteed.

SLC is not commonly used anymore in consumer products because of the higher price and lower memory density, but can be found in older flash devices as well as commonly in CF cards.

While SSDs use technically the same memory they have a much higher endurance. The reason for that is not a difference in the cells used, but overprovisioning. That means an SSD has much more (20-40% typically) actual capacity than is exposed as usable storage. That extra capacity is being used to dynamically reallocate blocks that have failed to fresh ones. The actual drive will only start to fail once all that extra storage has been used up. Neither USB sticks nor Memory cards have that (possible exceptions in very high capacity drives).

What counts for the endurance of flash memory is almost exclusively write/erase cycles. Reading has theoretically no influence on the longevity of the memory. The Limited lifespan comes from the fact that during every write/erase cycles an oxide layer gets slightly damaged. Once the oxide layer fails the cell becomes unusable. (this *can't* be prevented, it is part of the operation principle of flash itself) Reading does not contribute to the damage of that oxide layer.

BTW. USB connectors were originally designed with a lifespan of about 1500 insertions in mind. Interestinly micro usd was designed for a lifespan of 10-15k insertions. I have never seen a regular USB port break mechanically (unless SEVERLY mistreated) unlike micro USB ports which seem to be one of the first things to break on a device.

Flash can indeed get very hot, that isn't unusual. In fact, there are quite a few (generally PCIe or M.2) SSDs that come with heat sinks, because they get so hot that performance degrades.

If USB sticks or CD-DVDs are a better choice probably depends on the situation. USB is only useful if the target system actually has an USB port or at least a free PCI slot to add an USB controller (good luck finding that exceptionally rare ISA USB 1.1 card that used to exist) and an OS that has workable drivers for USB mass storage as well as the ability to use images (daemon tools, etc). If it is just about transferring data another option is plain old ethernet.

If it is about archival my answer is neither, get an external HDD.

I wouldn't recommend USB sticks, CD/DVD, or external HDDs for safe archival purposes.

USB sticks and HDDs can just randomly die from just sitting there. I've had it happen on multiple occasions.

CD/DVD is probably the most reliable out of those 3 IF you keep them stored in place where they won't get scratched and where fungus cannot get to them as it can eat away the metallic layer. And CD/DVD discs can also start separating after a few years if you buy junky ones. And IF you do use them for archival purposes, make sure to burn them at a much lower speed than they are rated for. The lower the speed they are burnt at, the better the burn. I usually burn CDs at 16x and they generally work fine in even the really old drives. DVDs usually get burnt at 8x.

The best option for archival/backup purposes is to have a local backup and to have an offsite backup. For my local backup, I back everything up to another computer and then to a cloud service. I use backblaze for my offsite backup as it offers unlimited backup for the cheapest price I have been able to find.

Backblaze is cheap for a reason. Have you ever restored files from backblaze? It is either supremely inconvenient or expensive and inconvenient. At least for the personal plans. Your restore options are either web download in 5GB chunks, which is painful for any significant amounts of data, or you get sent an external USB/HDD with up to 4tb for a significant fee. While you can return the HDD for a (partial IIRC) refund of that fee, that is only a reasonable option within the US (international shipping, taxes, duties and all the paperwork involved).

Offsite backups are all well and good but they are either expensive, really incovenient, quite limited or any combination thereof. Particularly if you have large amounts of data.

So, what do I do? External HDD backups of the data on my actual hard drives and archive of stuff I don't care about too much just on external HDDs. Offsite backup is just not a reasonable option if you have a lot of data and/or you are not within the US.

Well if you don't have a fast connection of course it is inconvenient. But it is still better than losing all your data due to a fire/theft/hardware failure/whatever if you don't have offsite backups.

The first time you have a situation where you have needed data lost, you will change your tune as far as offsite backups go.

it is not the connection speed (I have 100/40Mbit) but I have consolidated my hard drives on 8TB HDDs. I definitely DO NOT WANT to downlod multiple terabytes of data in 5GB chunks. Manually, I might add, there is no way to automate the process.

So, unless the offsite backup software has a restore function directly in the software it is functionally unusable as far as I am concerned.

I considered Backblaze for it, but I was smart enough to test a restore during the trial period. I canceled immediately after.

If you have significantly smaller amounts of data it might be feasible but for someone who can reasonably called either a Power user or a data hoarder it is not an option.