Poll: do you use scheduled scans for malware?

An  interesting comment recently appeared on my older post about whether or not to use antimalware software. Peter van Dam wondered whether scheduled scans are really necessary, given that anti-malware products scan files as they enter (and sometimes exit) a computer.

He raises a good point, and I’m curious what all of you think? Do you use scheduled scans? If so, why? If not, is it because you’ve decided the same as Peter?