ive not had a single HDD go bad on me......strange....ive got drives that are from 1 to 10 years old roughly and they all still work....
Thats why i said its all about luck. I was in the same boat as you up until last year i never had a bad drive before.
Then last year my seagate 7200.7 (If i remember right) drive died out of nowhere just stopped being recognized so i RMA'd it and the replacement had a high pitched whine to it, RMA'd it again and sold the replacement to a friend. So i replaced it with a hitachi deskstar and 2 months later it started randomly clicking and would lock up my computer until it was done with its temper tantrum. RMA'd that one and here i am 6 months later and the new one is starting to click again except this time its just a backup drive and is not locking up my system i just cant access it while its clicking.