There are many theories about this, and in fact some of my teenagers believe they are already there, or are about to be. But I submit to you that it doesn't truly happen until you find yourself doing several things:
-Buying a house (we close in on a house next Monday, hopefully)
-You are sitting at a red light in a volvo station wagon filled with car seats, strollers, old cheerios, and plastic toys listening to NPR and wondering if your 3 year old is old enough for soccer.
-You consider 7am sleeping late
I guess I have actually made it to adulthood, about time at 30 some would say. What's left? Grey hair, false teeth, and grumbling about the price of gas? Oh, wait, I'm already doing the last one! Ackkk....