I can't remember the writer's name and didn't hear all of it but one of the things she said was that marriage as the sexual and emotional fulfilment of a lifetime is a modern phenomenon. It was always an economic arrangement with love being secondary. Nothing new in that idea - I don't think it's that surprising to anyone.
If marriage was 'invented' to simply keep money/land safe, produce offspring, maintain status, it could last forever in the same was as any business partnership could, as there were no emotional requirements attached.
We have different expectations today. We want passion and fulfillment and excitment. But if that is the case, is marriage still fit for purpose? Can you really love and desire and find fulfillment from the same human being for ever and ever amen?