I have some small USB drives from that era with SLC rated for 10 years of retention after 100k cycles, meaning a 64MB drive has a total endurance of 6.4TB. True binary capacity too, with no wear leveling either, as only the spares on each page were needed for a simple ECC.
Too bad planned obsolescence got in the way, or we would've ended up today with bigger SLC drives that are fast and simple and just as reliable.
There's no planned obsolescence for my use case. I've never done enough writes to wear out an SSD. While I might buy an SLC flash drive if it was properly available, for internal drives TLC has barely any downsides. I very rarely get limited to 500MB/s, I need to turn it on sometimes, and I get 2.8x the space. Sounds great.
tl;dr: worn flash shows severe degradation, but more worrying is that there are even signs of retention failure with TLC flash that has been programmed only once.
Worrying if you want to leave it unpowered. I made that an explicit part of the tradeoff. I don't value that feature very much, and I don't think many other people value it much either.
It's important to make people aware of that problem, but they can solve it in other ways.
I'd pay an extra $20 to upgrade a 0.25TB flash drive to SLC and get unlimited retention. For a drive in my computer, I don't need it and it would cost far more.
Edit: I could even get an extra hard drive just to act as a backup, and TLC+HDD would still be half the price of SLC.
Good TLC/QLC drives will likely store your data as SLC if you overprovision them badly enough. (I.e. use only one fourth or less of the rated storage, since QLC stores four bits per cell. You can sort of verify this via benchmarking, since the SLC "mode" has far better performance overall.)
Too bad planned obsolescence got in the way, or we would've ended up today with bigger SLC drives that are fast and simple and just as reliable.