Don't keep your backup tapes in a secure place. Your backup tapes are possibly more valuable than your computer itself. They should be locked up or stored in a secure location. If you don't, disaster could destroy your computer and all your backup data. Don't rotate your backup tapes.
Some users always use the same tapes for each backup.
They simply write the new backup data on top of the old data. It might save them a few bucks, but it can cost a lot more later. Using the same tapes becomes a big problem if your system fails while doing a backup. In that case, you'll be left with a crashed system and no backup data. All it takes is a lightning strike, a power outage, or an accidental press of the reset button.