Are you leaving the cartridge in the drive all week? If yes, what happens during a true disaster? Fire, flood, anything that could destroy the Server.
If you do a full backup on the weekend, and incrementals during the week, what happens if you experience a Server loss on Friday? You will lose a whole week, unless the cartridge is removed each day.
If it's possible to add more drive space to the Server (internal or external), send the backup jobs to the new drive(s). Drives are cheap, so you can keep two weeks or more worth of backups on the Server.
Once the full backups are done, put in a cartridge and dump the backup files to the cartridge, then put the media in a safe or move it offsite. For each day, take the cartridge back, and dump the incrementals to the cartridge, and put it away again.
This kills two birds with one stone; you won't lose (up to) a week's worth of backup during a disaster. And remember, a disaster can be natural (like listed above) or man-made (deliberate or unintentional). The other bird is where there is only one copy of a backup job. If that single backup gets lost, corrupted, damaged, you're back to square one...losing up to a week of data. If you have two copies - one on the Server, one on the cartridge - you are better covered.
Dave T.