If this is a backup, you don't need it to be powered up and available 24x7.
So the question becomes more like "how long does an average hard drive last while powered down and still reliably be able to power back up and be read?".
I'm fairly sure that is a lot longer than the single digit years that'd be the probably answer to your question.
I wonder if there are useful guidelines for long term storage of powered down hard drives? My gut feel is the major failure modes would be electrolytic capacitor failure, bearings sticking as the lubrication ages, and obseleting of the interfaces. I wonder how hard it'd be to find hardware that'd read my Mac SCSI hard drives from 25 years ago?
So the question becomes more like "how long does an average hard drive last while powered down and still reliably be able to power back up and be read?".
I'm fairly sure that is a lot longer than the single digit years that'd be the probably answer to your question.
I wonder if there are useful guidelines for long term storage of powered down hard drives? My gut feel is the major failure modes would be electrolytic capacitor failure, bearings sticking as the lubrication ages, and obseleting of the interfaces. I wonder how hard it'd be to find hardware that'd read my Mac SCSI hard drives from 25 years ago?