Does a HDD lying in my desk degrade with age (or is its service life driven only by usage)?
If yes, are there publicly available statistics relating to any drive degradation when inactive for long periods, or engineering principles from which reliable estimates could be derived?
I don't know that there's data, but the general failure modes are spindle bearing wear and media damage - neither of which will occur in a powered-down drive of modern design (self-parking heads). As long as the drive is stored in an environment within manufacturer's specs, the drive should remain physically usable for decades. Stored data may fade over that time scale, however; if data preservation is the primary goal, it's probably sensible to connect the drive and perform a backup/restore cycle every year or so.
