You didn’t answer the other questions (or subtly hints I dropped) which may account for the duration of the scan.

  • With a resident on-access antivirus like avast, the need for frequent (or deep) on-demand scans is much depreciated. For the most part the on-demand scan is going to be scanning files that would be otherwise be dormant or inert. If they were active files then the on-access file system shield would be scanning them before being created, modified, opened or executed.

I have avast set to do a scheduled weekly Quick scan (more out of old habit), set at a time and day that I know the computer will be on. If for some reason my system wasn’t on, no big deal I will catch up on the next scheduled scan.