Han left after Ben turned to the darkside and betrayed Luke, he would probably be about 8 or so to be able to do so, or at least I think so, I could be wrong
Well VII takes place 30 years after VI, right? So let's say that Ben Solo was victory sex after the Empire fell, so he probably would have been around 16-18 when he betrayed the New Jedi Order. That still leaves 12-14 years of Han and Chewie off dodging responsibilities.