I think that people who have completely overcame the stutter have left it in their past life, buried it deep, moved on and never looked back. My sister overcame it in her 20s by never letting it get in the way, always putting confidence and goals first. Ever her posture was screaming confidence. I have heard different stories and ways of overcoming it that worked for some, but not for everyone. Also, there’s a free pdf online called “Speech is a river” written by a lady Ruth Mead that overcame it in the early 30s. It was one of the best stories regarding stuttering I have ever read, describing the exact emotions that many of us go through in a witty and genuine way.