Are you sure the Scan Service isn't crashing and failing to scan it at all?
I'm in the process of trying to figure out why our Scan Server constantly crashes after upgrading to 11 (I do have a ticket open, and they're looking into it). But from what I've found so far, mine crashes when I scan something by IP. but I'm still trying to trace it down. Not sure if its exactly due to it being by IP, or if its just non-windows items. As our Windows PC's & Servers pulled from AD seem to scan just fine. But Printers/Linux devices lock up the scan server service.