Generally, I do one big per season cleaning: we sort of coast along in between, with me trying to keep things from approaching biohazard level. Then I'll get a wild hair up my butt (you can usually time these to Holidays or Impending Maternal Visits) and suddenly it really, really matters if there's dust underneath the bathroom sink.

Vinegar cleans almost everything you can imagine. Although it's good not to use too much, or your house will smell like pickles.