Hi Hya,
I do the Quick Scans more often, that is with MBAM and SAS. The full scan just once per month is a good rule of thumb. Also I perform a Quick Scan with DrWebCureIt latest updated version once every fortnight,
important is to keep all your anti malware scanners fully updated and patches, I do that every day (some update automatically_ with avast, TrendMicro RUBotted, Comodo BO Clean, MBAM, SAS, SpywareBlaster,
and have an occasional look in event logs with EventLog Explorer, also update all my in-browser security add-ons/extensions in Firefox and flock browser: firekeeper, CSP, NoScript, Perspectives, RequestPolicy, FoxBeacon, CookieSafe, DrWeb's av link scanner add-on, finjan Secure Browsing add-on, and that sums it up so to say, OK, and also my firewall is updated automatically, for checking all the other third party software updates I use Secunia PSI,
polonus