im sure deep down you know when its over.. me and mine have both agreed if any of us ever feel like that then we will just end it. dragging it out would only be years wasted were we are willing to accept our lot but not trully happy.
i would rather we moved on and be happy, be it with another or single. if the rot sets in you could end up with hate for each other and that would be a shame
good luck with it.