You would have to check with support, but last I checked, they hold several backups, perhaps as much as a month. Unlike a typical third-party backup solution, you don't have direct access to the repository/catalog.
On-site NAS is an excellent part of a holistic solution. Send the off-site backup, send the backup to the NAS, and then do manual directory clean-up once a month. It is a bunny trail about our reasoning, but we recommend that you hold on the backup for the first of each month.
And while you are being anal, I on the other hand am only being professionally paranoid

Or, as I have learned to say, I'm a recovering engineer.