Hello, I also have Dell 124T auto loader and here is how I configured it.
On Management -> Libraries -> select your 124T library and on upper ribbon select
Optimize usage button.
I think you can configure what you need there.
If you select protection group set and choose Modify you can play with
Advanced button - here you can set write period - so if you set 1 day then after daily backup it will go to offline mode (it means even if on tape is only written for eg. 100 GB it will not allow to write next backup on this tape until your
backup will expire).
Other useful think there is to collocate different protection groups on one tape to save some tapes.
Good luck :)
