[acqq]

Note that that "proof" is not proof at all. Ignoring that it's anecdotal evidence on the sample of one, the author didn't have the checksum of the data on his SSD and didn't try to recompute it, he just tried to boot the computer with the SSD after being turned off for some time and then installed the new OS.

Note that the older the SSD (from the technology standpoint) the better retention is to be expected as the miniaturization of the data cells (which sinks the costs and increases the capacity) significantly lowers the chances for the retention. So his old SSD can behave better than the new one. And some lost bits don't mean that he can't boot, as long as it's just on the places that don't change the behavior.

[pmontra]

More anecdotal evidence.

I have two very old SSD. They are the 4 and 16 GB SSD of the early EEEPC 900 Linux version https://en.wikipedia.org/?title=Asus_Eee_PC#Eee_900_series

Needless to say, that netbook stays shut down for months but it still works when I turn it on. It survived many summers at 30 C. I don't know which kind of SSD it contains but being from 2008 it shouldn't be anything too fancy.

[acqq]

As I've said, the older SSD (technologically) and the lower capacity it has the better retention is expected. My 256 MB USB stick also still works, but one I've bought much later, 16 GB, died after only one summer of being not used. And that anecdote too really doesn't prove anything. The worst events are when just a few bits are changed and you don't recognize. Then a few bits more are changed... etc