How to be supportive, Is it too late for an adult to go to speech therapy classes?

How to be supportive, Is it too late for an adult to go to speech therapy classes? I am new to Reddit and just discovered this sub today as I was searching for information on stuttering. My SO has a stutter andI really wish I could help him. He took a couple of speech therapy classes when he was in high school, but stopped going. I think I will sound stupid asking this.. but is it too late as an adult (he is 29) to start taking a speech therapy course? Are there techniques that we can do at home and how can I be more supportive to help him with this issue? TIA 🙂