@ Terry209
Personally I feel that on-demand scans really are of little value with an on-access resident antivirus - and I extend that to the Not so Smart Scan.
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.
I used to have avast set to do a scheduled weekly Quick scan, set at a time and day that I know the computer will be on. But I have ceased this practice for some time now, based in the above.
That said the choice has to be yours, I have just run a Not so Smart Scan and it didn't take that long. I feel that much of this scans reason for being to to hope you will purchase other Avast products based on what it finds in the Advanced (my backside) Issues element.
You could however create your own Custom Scan and base that on either the Full Virus or Quick Scans, so you don't get all the other stuff you don't want.