I draw the line at the point when someone has a stable job that allows them to pay rent. I've seen people who basically had "two youths" and they were generally unhappy.

I’m interested in your experience. I injected a “second youth” into my life when I was around 30. I found myself having saved an incredible amount and as my above post implied I had my nose to the grindstone from 16-30. I spent a few years traveling the country, learned guitar and piano, went to massage school, produced music, had some brief affairs, worked at a beeswax candle factory, bartended, partied with drugs for the first time, and spent a whole summer making friends at the beach.

I learned so much about myself and the world and I wouldn’t be in the place I am today without my “second youth”. In a sense I gave myself the college social experience but I had an additional 10 years of wisdom to rely on (don’t follow the dealer to a second location, etc.)