When I was in grade school, I don't think stuttering bothered me too much. Around the sixth or seventh grade - and puberty - I really shut it down in school. Any time I talked in public like that I would be guaranteed to stutter badly, so I just never raised my hand. My grades were bad, I didn't go to college, and I got jobs that didn't involve much talking.
When I was in my thirties, I had a girlfriend who was in medical school, and I think that inspired me to start taking college classes. By that age - 35 - I was more confident, and I raised my hand and entered class discussions all the time. I still stuttered, but I generally had that kind of near-fluency, with pauses and minor, passing blocks that don't really stand out. I took a philosophy class that required a five minute presentation, and I don't mind saying mine was one of the best.

I ended up going to graduate school, where there are a lot of discussion groups in classes, and I talked all the time in lab meetings and even did hour long presentations of my work to the department each year.
I'm 55 now. I'll stutter until the day I die, but in many situations, I'm sufficiently fluent that my stuttering is trivial to me. Doing telemarketing for a living would be tough still, but during the summer, I lead hour-long local history tours for 10-15 people, and while I do actually stutter through the talk, it always passes quickly, and people always enjoy the talk and thank me with big smiles.
So my success is not from therapy - I stopped therapy about 45 years ago. My success is just from living long enough. I didn't to anything, I just outlasted the worst of it. Woody Allen said success is 80% just showing up. For me, success has been 100% just getting old.