the cms that gives different updates depending on how long people have been a member or how many times they log in is http://www.updatem.com/

i have not used updatem, but i have talked with them. they figure even if the cms portion of their script isn't right for everyone, it is easy to use the feature that shows the updates differently to different people with OTHER cms's.

seems like a good script, but i've only talked to a few folks who've used it.