I recall hearing that even at American Independence, marriage lasted on average 12 years for the same reason: somebody died. A widow needed someone to support the family economically; a widower needed someone to care for the family--him and the kids and any other household dependents of which there were likely several. The idea of pursuing/enforcing 'til death do us part' for decades on end is a modern challenge not faced by our forebears even a few generations back. Should have been mentioned in the Constitution, but neither were a lot of elements like earth, wind, or fire. Just a part of life as it was at the time.