I am not sure if the information below directly answers the question.....but I think this statistic does give some insight and encouragement.
I think it's safe to say it's a low number of these relationships that succeed long term.
A lesser known fact is that those who divorce rarely marry the person with whom they are having the affair. For example, Dr. Jan Halper’s study of successful men (executives, entrepreneurs, professionals) found that very few men who have affairs divorce their wife and marry their lovers. Only 3 percent of the 4,100 successful men surveyed eventually married their lovers.