Is there a tool to advise how much wear the drive has seen? (I've just acquired one and don't know it's history.)
As the cause of write-cycle limits (10k to 100k erasures ∓ a large factor given loose manufacturing tolerances) is a quantum mechanical effect, not even Werner Heisenberg could tell you with certainty when a cell will fail.
As a general rule, flash controllers have improved significantly over the last decade, with older drives doing less (or no) wear leveling.
If you are talking about a thumb-drive, the USB connector is rated for 10 times fewer insertions than the flash erasure cycles. If you are talking about an SSD, you shouldn't have to worry about it for another five years, at least.
Not quite what I was after but better than nowt...
Flash card/drive tester allows testing of any removable media including SD, MMC, CF, USB flash pen drives for bad or unstable sectors. Especially useful for testing for fake sizes often seen on low quality USB pen drives.