I think the average age was about 18-19. Charles Beckendorf was at least 18 since they mention he had been applying to college.<br/><br/>I assume most try to find a life in the demi-god world, but a lot of them try to live mortal lives once they leave camp. I imagine that a lot of the Gods have need of assistants for their mortal jobs. I can see Hermes having a mortal delivery service and hiring demi-gods to run it. Things like that...but yeah, I think about 19 they kicked them out in the books. I doubt Chiron would really turn any of them out if they really still needed the help or if they wanted to help out at the camp.