So there may well not, in fact, be A marriage for the same couple, but multiple, overlapping marriages.
If you apply this to your hypothesis about the divorced "in situ" (me pretending to know what the heck you actually meant here), when divorce was not so socially acceptable and easy, it seems likely (and verifiable based on conversing with old couples) that marriages live and die just to breathe again all the time when given time...as in my parents who have now hit a sweet spot of sorts in their 60s despite the fact that 20 years ago, I wished they would divorce because they seemed so miserable.
How one views marriage as an entity has everything to do with survival rates, sometimes it leads to spouses taking each other for granted but I submit that it ultimately leads to hitting a sweet spot and having the kind of intimacy and security that comes from surviving the lumps and bumps together over a life time (separations included).
And by the way, cancer is on the rise...and so is divorce (but we can debate this another time.
