You're already doing the right things and asking the right questions. I've been in speech therapy since I was around his age as well (31 now) and it really does help, though it's possible and likely it will never go away. But I went through a Bachelor's and Master's, teach college classes, and have a wife now, so I would say if you give him tools to help and make it manageable, it shouldn't limit him. If I were to pick two important things to keep in mind it would be these: 1. The goal shouldn't necessarily be to not stutter, it should be to be able to communicate well and confidently. 2. Try and get him to open up about his speech, and even to other people. It really does help to be able to accept or even embrace it a little. Find a therapist he likes, and just keep him working on it. The stutter might even go away, but if it doesn't he'll be totally fine if he keeps up the work and stays positive about it. This is just my opinion from my experiences, but I hope it helps.