avast already has that feature it’s called the “persistent cache”. Once scanned a file won’t be scanned again unless it has been accessed.
As far as scanning archive files, what’s the purpose in that? Archive files are by nature inert and don’t need to be scanned. Once “any” file is
accessed the file shield will then scan the file using the latest and most up-to date virus definitions. With v2014 avast implements “continuous
streaming updates”. Continuous streaming updates are released approximately every 3.5 to 4 minutes.