It's not about losing the drive: hard drives break all the time. Externally cased ones especially as they are subject to many more shocks on average. Drives that haven't been spun up in a long time are even more likely to fail upon spinup.
This is a good point. I was thinking that a drive rarely turned on would last longer than the usual 2-3 years...but it's a bit of a worry if you don't know if it'll turn on at all after 5 years.
I have an old Lacie Rugged 160 GB external drive that's 4.5 years old, and rarely used. It had a 1 year warranty. It's still working. I don't rely on it totally these days, though.
