I have a 5 year old Seagate USB2 drive for backups, used for a few months with time machine on my Retina MBP.
Lately, I've been getting an error that it was improperly ejected (I didn't actually eject it), and I can hear the drive churn endlessly on its own. I can't remount it, its power button doesn't respond, I have to power cycle it, then it mounts again and seems to work. Until the next incident.
Is it dying on me? It's old but has only been lightly used, until recently.