Curious... I thought that the built-in drive controller chipset already handled "wear-leveling" internally and transparently to the user.
I did do a little research, and the common failure mode for over-used NAND blocks, is that files will become "READ ONLY"... thus, allowing you to still retrieve them for backup/copy to a new drive. It would have been nice if THAT was the failure mode, here... my backups were good, but older, so a small amount of data was lost.
Gotta make more current backups, more often. ;)