YEs that's right. If you put all your media in the scratch, then once the backup is done, it will put the tape in the media set you've specified. I would allow infinite append as you have and also put a 7 day overwrite protection if you are having one tape per day for example. The backup will finish put the tape in the media set. The next day will grab another tape from scratch, do it's stuff and then put that into th media set and so on....
Then after 7 days it will look for a tape it can either append to, or one it can overwrite, but the data will be proitected for 7 days reagrdless.
If you put your tapes straight into the media set to begin with, it will instantly take on the 7 days protection, so you can't use any of those tapes for 7 days. That had me stumped for a while!!!
If you want to use specific tapes for specific days, you will need to look at partitioning on the Backup exec help files.
Hope that helps