Scrambled eggs for brains. That is what I was told every time I asked these why questions. My tells me constantly he wants a divorce (without using the word) but won't file and won't even tell me what he doesn't like about the separation agreement I had drawn up.
If you read the stories from a lot of the returners they say they knew they'd come back in 5-10 years whatever. I think they try to keep their place at home while they are out running around living the teenage life. Let him pour his money to improve a house he doesn't live in.
Forget about him and live as though he isn't coming back.