What Avast Program and version number are you using ?
Whilst I would agree it is important to keep your antivirus program up to date. I would question the need to run a Smart scan every week ?
With a resident on-access antivirus like avast, the need for frequent 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.
With the Smart Scan is it stalling in the 3rd Advanced issues, this is generally related to vulnerabilities/weaknesses in your protection. For the most part this is Avast pointing out potential issue, only to offer you a solution (paid product) to solve it.
So in your previous scanning for Advanced Issues what has it reported ?