I manually update all my security applications daily. Run SAS, AVG-AS and a-squared (alternately) when I don't use the computer, run Ad-Aware (twice a week) and Spybot (once a week) when they are updated. Once a week a scan with Antivir, regularly a free online scan (Housecall, F-secure, Nanoscan/Activescan, Kaspersky)