I try to single primary ferment for 3 weeks, give or take a few days but I dry hop a lot and feel the 3 weeks help.
Also, when I've fermented for only 2, I've found my beers to green and I have longer time in the kegerator. Bottom line, either way for me, It's usually about 4 weeks from boil to first, good, tasty beer.
Sometimes I naturally carbonate but I'm quickly moving past that.