I feel like this is a research project for a speech therapist? Regardless my stutter never left. Anxiety is the biggest factor on how extreme my stutter will be. Confidence suppresses the anxiety so if im more confident im less likely to stutter. I stuttered less in my teenage years but I tend to stutter more now that im an adult but again that was a confidence thing. Im not so confident now a days but that doesn’t directly relate to my speech it’s other factors as well. My grandpa also stuttered and his was pretty mild if not better than mine though he did experience blocks. However he was very social and had several friends so I feel like he built his confidence that way and through the huge family he helped create.