Apparently some small percentage of couples do experience this. I don't think it's some magical "marriage made in heaven"; my theory is that some small number

Apparently some small percentage of couples do experience this. I don't think it's some magical "marriage made in heaven"; my theory is that some small number of people have a superhealthy relationship with their ego, and so don't need to differentiate (which is what causes the honeymoon-leaving), and if you get two of them together, they can stay in the honeymoon state indefinitely.