When I was a young lawyer, with far less gray hair than I have now, I remember citing, Lepis v. Lepis , the seminal New Jersey case on modification of agreements or orders, for the proposition that “contract principles have little place in the law of domestic relations.” And that seems to make sense because you are dealing with people’s lives, children, careers, loss of jobs, etc. Seemingly that is why the concept substantial and continuing changes of circumstances being required to modify something.