Another approach would be this, assuming that you are backing up to other drives in your office (we use another internal hard drive, an external hard drive, and a 2nd hard drive on another PC)
From time to time, (I try for weekly), after opening AC backup, click "Advanced settings" then uncheck "Use AC offsite backup" and "Exclude imported items", then run backup. You will then have imported items backed up in all on-site locations.
Just remember to return to usual settings after process is complete.
Gene