Stats are quite conclusive. If you are still stammering when reaching adulthood you are pretty much stuck wit it. I think there is a about a 3-5 year window for kids to "lose" there stammer once they get it. Otherwise its likely to stay. I myself am an adult stammer and I am well aware. There are good speaking days and bad. Some days, months, weeks I won't stammer at all hardly... then others, it's not the same. Swings and round abouts