djmiketjg: Although I wonder - do your drives just go kaput completely or do they just start struggling to read certain data?
Pardinuz: They never go completely kaput, usually they just struggle to read data and get bad sectors. It has also happened to me that they can't write or delete data but they can still read it.
Actually I use them very seldom, it's not like they're spinning for 2 years non-stop. I guess lack of usage could cause problems too.
It's certainly interesting - drives are supposed to be able to deal with this but the odd drive I've had that go bad was reading and writing perfectly fine until it hit a sector/sectors it struggled with, then all of a sudden the drive would become incredibly unresponsive. I'm unsure whether I simply needed to leave it to sort itself out - HDDs will try to recover stuff to the 'spare sector' area which is there to allow for problems like that - or whether the drive had simply run out of recovery area and was just stuck.
I suppose cloud storage is a way to go for backup storage (I've certainly considered doing this for data I don't want to lose) but I'm not sure I want to surrender all my private data to the ether of the internet. :)
My current solution is to have a 500GB partition on two HDDs with 'important' data, that I then use a manual process (NOT RAID) to backup from one to the other occasionally. That way, if one drive does go I have the other with a recent backup to take its place. I only avoid RAID because that means I also have a restore point if I delete/mess up the main drive!