Ex's are ex's for a reason, as others have said. I have two very significant ex's, both of whom I much later re-established contact with (one at my initiative, the other at hers). They both emigrated across the Atlantic soon after we finished ... must be something about me.
Looking back on it, one was the right woman but at the wrong time. The other was never going to work out longtime, and the recent contacts confirmed both cases.
The other ex is the ex-Mrs Muttley. I have occasional contact with her, and it's much less than it was since Muttley Jnr grew up.
After we sold the marital home to buy our own places, I had the ex-Mrs lodging with me for a while. I kept putting Pink Floyd's "Meddle" on the CD player ... there's a particular track called "One of these days I'm going to cut you up into little pieces."