As of today I've worked at Microsoft for four years—four years of having a real job, being a productive member of society. That's longer than I spent in high school, longer than I spent in college.
It hit me an hour or so ago that, in a capitalistic society, couldn't you theoretically pinpoint the time at which your impact on humanity has been a positive one? It would be something like the time at which the amount of wealth you've generated (for anyone, not just yourself) was greater than the value of the resources that have been used to keep you alive, educate you, and so forth. Does that work? Realistically, you could never calculate that time because there would be an infinite or near-infinite set of numbers to add and subtract. But it seems that if everything in the world could have a dollar value associated with it in terms of resources and services used versus consumed, you could find exactly when you became a worthwhile investment.
But then again, I don't really get theoretical economics.