Long-distance is perfect for extramarital affairs. Distance shields the other person from EVERYTHING negative (schedules, family commitments, etc). So does ANY extramarital affair. So (in my opinion) an affair that may appear to be hampered by distance is in fact aided by that distance. It's ALL icing, no cake.
So I agree that having the paramour relocate closer could be a good thing. My wife's OM is planning to move about 300 miles to be with her. I found this out last night along with another important detail, that she is VERY insecure with their relationship and she is afraid of losing him. She is very clingy, and says, "tell me you love me" A LOT (how I found out is a looong story).
To most men, insecurity such as this is very annoying. I am confident he will quickly tire of it. Couple this with my sterling DBing (thanks in large part to my circle of friends here), and I have reason to be optimistic about us fixing things.
My job now is to appear to be a stable, constant source of support to her. I can be somebody that she can count on without having me tell her I love her over and over. This won't be easy, but I am up to the challenge.
