IF all you want to do is use each slot in order, you could do as suggested and create a partition, or you could just use one Media Set, with an Overwrite Protection Period of 8 days and one job, defined as overwrite
When you load up the library, label each tape in the order that you want them to be used, then just let BackupExec and the library grab tapes as needed
This way, if your job ever exceeds 1 tape, the job will just grab the next tape in order and continue
Personally, I would rather set up two jobs, a daily and a weekly, then take the weekly off site (even if it just goes home with me). This way. if your building burns down, you can recover back to your last Friday backup.
(I guess you could do as you plan, and just export the tape each Monday morning, and insert and label a new one)