Like Grim says, it's not just about maturity. Are there mature 17, 18, 19 year olds? Sure. I'd like to think that I was one. Having said that, I don't think that my 19-year old self and the current mid-30's version of myself would have much in common. I mean, how many teenagers would care in the least about the latest strategy I'd devised to keep my kids from fighting in their carseats? And I, correspondingly, am many years past caring what happened to you at your latest kegger. Like Grim said, it's about how we relate to each other.