From my experience with the kids.... My research basically focused on ex-gang members, so they had to exit the gangs to participate in my research. When they enter the gang early, at about 10 or 11 years old, they will exit at 15 or 16 years old. But those who enter late can go into their mid-twenties or later.
What I noticed in my research was a pattern. I called it a “life course” development. The life course development was as they grow, they mature: their physical age, their biological age, but also in their life in the gang. The first phase is attraction--fun, activities, parties, and everything. Then it becomes more demanding. That is the time when they think they need to get out, that this is not why they came here in the first place. That's the maturation phase.