Lets not lose sight of the fact that ‘any’ on-demand scan is for the most part going to be scanning dormant or inert files.

Since avast is an on-access scanner files that are ‘active,’ being created, modified or run, etc. will be scanned. This act depreciates the need/value of on-demand scans.

Archive (zip, rar, etc.) files are by their nature are inert, you need to extract the files and then you have to run them to be a threat. Long before that happens avast’s Standard Shield should have scanned them and before an executable is run that is scanned.

Me I have a weekly scheduled Quick scan and a monthly Full System scan and for me that is more than adequate.