malwarebytes?

A quick scan twice a week for me, and a full scan once per month. I also scan twice per week with HitMan Pro.

One piece of advice i got from Malwarebytes (either their support team or the forum, i don't remember) was to always perform the scan with admin rights. Only for checking the registry system the scan should be done from the appropriate user account.
I don't know for sure but this may be true for all AV scans. I am not an expert on this.

Every Sunday I do a full system scan and every second day I do a quick scan.