I’ve seen a lot of hard drive failures, but I guess that’s because I’m the one they call when they fail. And I’ve installed [boat]loads of new computers and have seen a few DOA drives. Come to think of it, I can only think of two or four failures at home. One was me shorting out a drive stupidly, one was probably heat related as I had three drives sandwiched and the middle one failed, and the other one or two were used drives my BiL gave me from a failed heavily used NAS, and come to think of it I was trying to use those on a couple of motherboards that I finally decided had both somehow picked up the habit of corrupting ATA reads and writes without detecting errors.
Oddly I’ve had two flash drive failures so far. One thumb drive that has been through the clothes washer and dryer a time or two seemingly works, but I found it was repeatedly corrupting data without indicating errors. Zip file checksums helped me figure that out. My 4g SSD in my eeePC (which hasn’t been in the washer) has a bad spot on it. I tried backing it up, but it always fails at the same spot. I think I can work around it, but so far it’s only preventing me from making a full backup so I can install Android or eeebuntu on it.
I suppose rotating USB drives might make more sense than paid network storage. I’m not sure it’s cheaper if I assume I’m not spending extra on high speed internet.
I suppose another consideration is privacy. USB backups at home are far less exposed to the random internet hacker.
As far as seldom-reused data, that’s probably right. I have I think all my emails going back 10-15 years. Part of me knows I don’t need the vast majority of it, but I can’t seem to let it go. On the other hand I do occasionally search the old stuff, but mainly for account and login information that I’ve forgotten. (“Do I have a YouTube login?”) Instead of formal documentation I tended to send long emails to coworkers, and I periodically think I should go back and scrub those emails for documentation and resume fodder. It’s sort of the same thing here; if I want to find some info on my current hardware at home there’s a few posts on this board I search for and read as opposed to having locally organized documentation.