To say you used to be a stutterer, is akin to saying you used to be an alcoholic. You either are, or are not. There is no cure. There are however varying degrees of fluency. Some people can go months or even years without an episode. Others can not go a few minutes. To say they are cured, or "used" to stutter, implies that they don't stutter or never stutter now. That is the BS component. There are no absolutes with stuttering. The environmental triggers for some are chronic and on-going. For others, there are no triggers and it just happens. It is an on-going and ever elusive neurological disease. If your father has become fluent to the point that he is cured, then he has obtained the golden ticket in life and is incredibly blessed. That would be an amazing, and life alternating turn of events for any stutterer.