Decent quality hard disks and DLTs will probably be fine. I've had DLTs survive 100oC for over an hour inside a fire safe in a fire and some old Seagate Cheetah 10K U160 SCSI disks in an external SCSI case with a dead fan running at 80oC for a month quite happily. The latter was actually running and operational which is remarkable.
Some optical media will fail. It doesn't even have to be kept at 75oC from experience.
Flash will almost certainly fail (leakage increases with temperature). I've had dead CF cards, USB sticks, SD cards, the lot and corruption after only a couple of years stored in ideal conditions. Then there's the old Sun PROM crapfest to consider as well...
These are all anecdotes, but there is data out there to support this as well.
Some optical media will fail. It doesn't even have to be kept at 75oC from experience.
Flash will almost certainly fail (leakage increases with temperature). I've had dead CF cards, USB sticks, SD cards, the lot and corruption after only a couple of years stored in ideal conditions. Then there's the old Sun PROM crapfest to consider as well...
These are all anecdotes, but there is data out there to support this as well.