I too have just completed developing a replacement backup process. The databases (around 45 of them across 2 servers, serviced via batch processing) are all BI related, and very occasionally a restore is required when we try to "undo" the impact of some bad data that has crept in. The old retention periods did us no favours (3 days) as we frequently wanted to go back to further - and this required requesting the return of an offsite tape which could take up to 48 hours.
The new regime holds online 4 weekly full backups, and 15 days of differentials - all held on a network drive which is offsited via the Internet. I'll tune the retention policy as necessary. If we need to restore prior to the first differential we can roll forward be reprocessing the raw data (also backed up) from the OLTP.
I mention the above because whilst your process is keeping the latest backup online, how long is it going to take to retrieve a tape if you need to go back more than the last backup on disk?
BI Technical Lead
Clear Channel International