alt Hacker NewsTapes were constantly kept in the data center, so constant temperature and humidity 25C/50%. As I said, Tapes were changed after N uses, drives properly serviced. So if you leave them at home, in the sun in summer and in winter expose them to 10C with humidity from 10% to 90%, old drives, never clean heads… IdK That all being said, when I started working there, in my ignorance, I said “TAPES?!?! They are not reliable” due to my experience with audio tapes. But I was laughed at, and they told me about people putting 10 9 track spools in a car [0] (by the way, the same we used for billing backups!) and they went literally thousands of miles driving on partially dirt roads, in summer w/o AC, doing updates to systems, and also never ever had an issue. They were so sure they would work, that they did not take a second set, even when driving 1000 miles, and a read error would mean going back!!!
Usually it wasn't the tapes that were unreliable, but the tape devices (firmware) and/or the drivers. Years back I used to work on a backup product - one of the tape devices would write a random amount of zeroes after each round of N megabytes written to the tape. So if you were "lucky" and all the backups were below N megabytes in size, everything worked perfectly. We weren't even aware there was an issue until some of our customers started complaining.
Debugging this was really fun, especially due to the randomness factor. :)