AthlonInside - 12:24 pm on Oct 30, 2003 (gmt 0)

The update is continuos, with slightly changes everyday. I believe it happens almost every day. Just because everyone's eyeballs are focus on a few terms (that related to them), they would feel like changes only happens once in a few days. Assume you have the sight of ALL people, minor changes should happened all the time.

2nd, there is a thing similar to the dance, the backlinks update. Also around once a month. But that's really quick and does not affect the SERPs much because SERPs is affected continuosly as I say.