I've got a 120GB that's been going for 4 years straight... it only gets a break when the power goes out or I'm upgrading my computer.
Does that answer your question? :lol:
Most hard drives have a MTBF (mean time between failure) of over 500,000 hours. That's over 57 years of reliability. Of course, that doesn't mean your drive won't fail within 5 years... it's just an estimate.
In all my days of computing, I've only had 1 drive ever go bad on me and that was back in the 100MB hard disk days when MTBF sucked. I had another go bad on me recently, but that was my fault. I dropped it. :-/
-mpjesse