Regarding air bending mastery and tattoos, the usual age for receiving one's tattoos falls in between 14-16, right? Aang and Jinora were prodigies, resulting in getting there's at 12 and 14(?), however, I'm uncertain when an air ended normally receives their tattoos. I know it's based on mastery, not age, but there has to be an average age when people master their element. Anyone know?