Didn't know until now that USB sticks could become useless altogether after years on inactivity. Is this also applicable to the sticks which are produced in the last few years? I have yet to back up my wallet in any USBs so this is a great piece of advice that I just came across with, for future reference.
Magnetism wear off after a while and the media it is stored on also deteriorate after a few years. If you plug it in and leave it for a while, the magnetism will increase and it will last longer. Just use a offline computer when you doing this, or your data stored on the device could become infected or even collected by a hacker.
In any way, this is how it was explained to me. I hope the guy was not pulling this out of his ass. ^smile^