I agree with the first comment, "green" beer is the result of off flavors caused be yeast reproduction and fermenation, such as acetelhyde, diacetyl, that are slowly consumed by the yeast as a beer ages. (the "clean up after themselves" phase")QUOTE]
This summer I basically filtered 5 gallons of Kolsch at .5 microns. This removes essentially all the yeast. If anything, this beer seemed to need less conditioning than the 5 gallons I didn't filter. So I don't necessarily think "yeast cleanup" has anything to do with green beer.
I use starters and control fermentation temps. My beer stil is generally much better after a few weeks in the keg. About a month is a decent time frame for me. 2 weeks to ferment. I pressure ferment, so after two weeks I crash cool and the beer is already fermented. It's often drinkable after 2 weeks, but even better after 2 more.