I don't run scans regularly - only when I've loaded something suspect, and only on certain directories - before and after I install it. And I do do some very suspect things

Basically I practice safe computing!
I get no value for full system scanning when the in-memory / on-load scanner is active anyway.
If you don't have a virus today, and you don't load anything suspect, you won't have one tomorrow.

Your best system defence is good regular multi generation / copy backups, not virus scanning.