My friend is using an old Maxtor 512 MB drive from 1994 that I gave him after I used the hell out of it, and the thing's still chugging along like a champ.
Since the new drives should be much, much better (technology- and dependabilty-wise) than the old Maxtors, your drive should last, let's see...135 years? :-D
I have a 20 GB DiamondMax that's about 1.5 years old and running fine, but it could die tomorrow. No way to tell.
I think they come with 3 year warranties, so at least you know that if it dies within 3 years you'll get a new drive.
"There's no such thing as gravity, the Earth just sucks"