Divorce Law Question - Future Earnings

I heard a lawyer/radio host commenting this morning on the pending Rudolph Guiliani divorce. He was discussing to possibility of his paying alimony payments, and commented on the fact that, at this point, Ms. Guiliani/Hanover probably makes more than he does. He suggested that R. Guiliani’s earning potential is enormous, as he can sign up with a top tier law firm at an enormous salary, and that earning potential can be factored into the settlement.

My question is this: suppose Guiliani does not wish to go to work for a top tier law firm, but prefers to work in public service or some other lower paying job. Is the earning potential that he does not intend to realize still to be factored into the settlement? That would in effect force him into a career that he does not want. OTOH, if it is not, what happens if he changes his mind and goes after the big bucks? Does the issue get reopened? And what of someone who is already earning a huge salary? Suppose that person decides (after the settlement) that they’d rather switch to a lower paying career. Do they have the option of re-visiting the settlement?