One of the other common practices, especially if you intend to have the data put to tape for longer periods of time than what exists on disk, is to use vaulting schedules.
So, in your policies, you can create schedules with names such as "Full-1mon-IM" or perhaps "Full-1year-onsite" in which you intend for the schedule to mean that you want the data to be considered for full backups to be duplicated for 1 month and sent to Iron Mountain or be full backups and exist for 1 year onsite as tape. You can then have the system backup to disk and have a retention of whatever short amount of time you want it to remain on disk (say 2 weeks as default).
Then go into your vault and set up different vault jobs based on the schedule name that would cause it to duplicate and then set it to whatever retention you want. I.E. there is a vault job that says 1mon-IM that says that whatever schedule names that have run with names "Full-1mon-IM" or "Incr-1mon-IM" or "User-1mon-IM" that they will be selected in the vault job and duplicated to tape set for 1 month and you can build procedures to email Iron Mountain about their contents, etc.
obviously there are a few more steps but if you need assistance i could probabbly put together a blog that contains a walkthrough of the idea.
