Anyone know a lot about them?

I've been trying to record digital TV programmes on one, and it doesn't seem to be able to take very long files. It's a good make, and 16gig, but after about one-and-a-half hours it seems to switch off, wait a half-hour, and then start recording the signal again.
Unfortunately, that means it misses the last quarter of one show and the first quarter of the next.....

Is there a thermal or other overload in the flashdrive, or will a bad sector do that? Do flashdrives have sectors? Is there a download that will check it out?
My 8gig one will just fill up and switch off.
Chris.