After a marriage of 46 years and counting, no doubt till death us do part, I’ll try to respond to your challenging poem with its amusing ironic touch. The best answer I am able to offer, can be found in one of the most beautiful songs I know.
It has been adapted by an equally famous (in my country and in Germany) artist with the name Herman van Veen. In his translation one sentence stands out: ‘if a love can last so long, it must be true love’. A hypothesis, only to prove after the fact. True love is a process. And, sadly, even true love can be damaged or destroyed by the sickness that is called infatuation. I know several couples that were seen as the prime example of true love, breaking up after someone else intruded. It takes two to tango.