I don't have children with my ex-husband (the marriage was celibate), so I don't need to really keep in touch with him. We still have stuff in storage in another state, once one of us (ie: me) gets enough money together to drive up and get it, so I only keep his email and phone number for that reason. We pretty much ignore each other's existence.
Although if he found another woman, I hope she has enough sense to realize that 44-year-old men should not have the emotional maturity of a 12-year-old, and that he will blame her for not being able to get it up because she's the one getting worked up about a "genital sneeze".