To know how many, or a percentage, we would have to know the total number of cases, including how many did not return, if they were wayward, walk-away, or MLC. And what space of time do you mean, like the beginning of time or since this board has been available, or what?
Since I have been on the board, I notice that the majority of people leave without us ever knowing how their story turns out. Then there are all those people who read but never post. In short, it is impossible to answer the question you asked.
It is not about what you feel should work in your M. It is about doing the work that gets the right results. Do what works!