Bob Hawkins,
Welcome to the forum.
You do not mention what product of Avast you have (Free, Pro, AIS). Regardless, there is no reason to scan your system daily since Avast is constantly scanning your machine in the background while your machine is on. In addition, you would not want to do a scan until Avast does a definition update. So if you are scheduling a scan prior to a definition update, this is fruitless.
Most users do Quick scans once a week, Full scans once a month, and a Boot scan only when you have an infection that the normal scan can not remove. The scans are all dependant on the user's usage. I personally do manual scans, but some people prefer scheduled scans.
So you may want to think about how often you are scanning since it appears to be too much since Avast is already scanning in the background. Let me know if you have any questions. Thank you.