Servers should backed up each day and the backup tapes should then be stored off-site. Individual PCs are not used to store critical data. Alternatively, there are network-based backup utilities that are designed to back up all data from PCs that are connected to the network. Just because you have a tape drive and a backup tape doesn't ensure your data's security, though. Off-site doesn't mean that you make a backup and then toss the tape into your car's glove box, either.
Some tapes are highly sensitive to temperature and most are sensitive to humidity.
Jeff Kettell, who manages the backups of all systems at Proficient Computing Solutions Corporation tried a test with a Sony DAT data cartridge. Jeff took a tape home, set the oven to 125 degrees, put a DAT cartridge on a cookie sheet in the oven, and waited. Within 15 minutes, he could smell the odor of melting plastic. Within half an hour, the cartridge had been reduced to an unusable blob. It's worth noting that this was not a scientific test.