If you have an autoloader/library, you won't have to worry about a tape loading automatically. It will do that like Ken said, as long as you have scratch media available in that device.
For the tapes you need to retain for 7 years, I would make sure your retention policy is set up correctly. You'd obviously need a minimum of 96 tapes. Once your retention policy is configured correctly, those tapes will be locked and won't be overwritten, unless you move them to another media set, or erase them.