How long is 'a few years'? Controlled environments shouldn't be necessary for unplugged drives, just keep them at or slightly below room temperature.
I've had three external hard drives for 7 years, and none have stopped working. I have one, and keep two somewhere else (office, family). I connect one for a few hours every week/month to update, then leave alone until needed, or rotated with one elsewhere.
I've had three external hard drives for 7 years, and none have stopped working. I have one, and keep two somewhere else (office, family). I connect one for a few hours every week/month to update, then leave alone until needed, or rotated with one elsewhere.