[allegory]

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.

[VLM]

"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."

The story goes back much further with solid state if you talk to "retrocomputing enthusiasts" unfortunately eproms reading all 1 awhile is depressingly common. You only need a single bit error of course for software failure.

Another interesting point to bring up is it is Very well known in the retro community that the details of eprom programming technique and certification (or lack thereof) of eprom programers has a dramatic effect on burn lifetime, like multiple orders of magnitude difference in burn lifetime. Anyone can make an eprom burner that verifies an hour later. Much harder to make an eprom burner that verifies 10 years later.

This affects more than stereotypical retrocomputing due to embedded devices. Plenty of PBXes and machine tool controllers and scientific instruments and classic video arcade machines get scrapped because the eproms lost their minds.

[allegory]

Very good points there. I worked for an aerospace and defence company for a bit as an electrical engineer. Our software was always read into RAM, checksummed, the RAM was write protected via a register and only then the code was executed. The bootloader was a mask ROM. That was all just to work around the possibility of bit flips in EPROMs.