Earlier quoted context omitted.
> because flash memory loses data over time if it's powered-off. That's a red herring; the magnitude of this effect is usually greatly exaggerated, and in reality never comes close to being as important as the fact that flash memory is simply too expensive to use for cold storage. And of course, the very idea of cold storage is dangerous: if you really want to ensure your data lasts for decades, you should be verifyi…
I remember reading something somewhere about a guy doing tests on "3D" NAND and other TLC/MLC NAND SSDs and finding that data was lost well before the "10 years or so" that we have come to assume unpowered SSDs can retain data for. I can't locate that article at the moment but it isn't unreasonable to expect faster degradation on denser NAND.
The SSDs that caught the most flak for poor retention characteristics were using the last generation of planar NAND, in a three bit per cell configuration, which in hindsight was a bit of an overreach. But even then, the worst symptoms that could be reliably reproduced were poor performance reading back stale data, a result of the drives having to use higher levels of ECC to recover the data. (More recent SSDs have vastly more powerful controllers capable of running LDPC calculations much faster.) That's not quite the same as losing data.