I agree with John about setting the protection, however, you can leave the Data Protection (which includes messages) as Permanent, or 52 weeks, but set your catalog protection to a quite lower value, lets say, for the sake of argument, 30 days
When Catalog protection expires, Daily Maintenance will delete the catalog, which takes up the most space, but leave Data information behind
I worry about your media in this case, because that is all going to have to be protected too. Are you looking to save EVERY message from every session, just errors, or a summary of your backups? There are a few reporting commands that you can run if you don't necessarily need to save everything