I can sort of understand a certain amount of financial reasons for forcing you to stay, but am unsure what legal reasons there could be. But I'm not asking what they are here. If you are empty nesters and both get no benefits from the relationship, I can't imagine why separating (living in different homes) is not an option. You could mutually agree to have "open relationships", unless you have some religious reason not to. I can't imagine why your wife wouldn't be wanting some more fulfilling relationship, too...possibly with someone else.