Regarding that 80% rate compared to a different outcome as you get older : I teach young children and know that they all have times when, for all different reasons, they speak w dysfluency. Most do not even notice it as a “difference/problem”, and IMO, that’s the main reason is goes away. It just evaporates bc it gets no attention. As it lasts longer and more attention goes toward it, it becomes an entirely different thing (that’s when secondary behaviors pop up, which simultaneously reinforce and worsen the original dysfluency). Also, I propose that a dysfluency characterized mainly by repetition is quite different once it develops into hard blocks and secondary behaviors.