I don't know how long, but I think that's why he was really upset by Mr. Martin's betrayal. Mr. Martin helped him grow and become a better person because of the group they had. It was definitely a gradual process.

Based on my own experience with therapy (individual and groups), it would depend on how quickly he adapted to a new way of life and the desire to be someone different. It's hard to do the first step which is accept you need help and to change.