Scheduling scans with Avast is easy, as it turns out, if non-obvious. Launch Avast, then, non-intuitively, click Scan Now. Click Settings, then, buried on the left is an option called Scheduling.
I recommend doing a quick scan at least once a day and a full scan at least once a week. If you’re using Avast as a secondary scanner, be sure to have your primary scanner scheduled to perform scans too.
I was explaining this to someone this week, and he said, “Wait. You wrote a book about performance, and you’re saying run two antivirus engines?” Yes. There’s minimal, if any, performance penalty to having Avast as a second one, and you get better security. Get an SSD, and you can scan multiple times a day and probably not notice.
Scanning at least once a day with two different engines protects you if one scanner finds out about a threat before the other does. When you can’t get perfect defense, you layer it to at least get something better.