Last year I bought a used 1TB SSD. Bad move. I partioned it and started using for various backups. Seemingly it works fine.
BUT, when I tested it with utilities, all tests showed bad blocks. Now, I know that certain amount of bad blocis can be tolerated - the SSD comes with extra reserve of blocks, and when one attempts to write a file on bad block, a good block from the reserve is allocated for it. So, there I have a 1TB SSD hard drive, with almost 50% of space used, most of the files can be read and often I can copy to it. But a utility like Disk Warrior tells me "all spare blocks have been exhausted". And I was able to locate some files which can no longer be read. Obviously, this dirve will be junked because I heard of no way of fixing it.

So, now I will have to buy a new one and obviously it will come from MacGurus. Ok, so I order one (1TB crucial) and do a full surface scan before I start using it. Most likely it will show some bad blocks but the reserve will be untouched. So I start using. Suppose in time, in a year or so, more bad blocks develop and I will come to near the end of the reserve. Will Rick replace it with a new one? I am sure he will, hopefully without any $ loss to him. But how do I return it? I would insist on total secure erase, perhaps triple pass with a utility like Drive Genius.

Rick, is that the way to go in case of failure? And one more question: if a file is sitting on a bad block, can it really be wiped out?

A curious observation: when I try to read the bad file from SnowLeopard, it tells me it is damaged and that's it. No problem. But when I try to read the same file from Sierra, most often the computer either freezes or shuts down, as if in kernel panic. But it restarts ok.