Since moving back to the Bay Area I've been out with four other people too, one of whom he's also seeing; I've been in my primary's presence while he kissed one girl, and when he asked another for her phone number; I've gossiped with a secondary about other persons of romantic interest and accepted his offer to hint to a guy I like that this is the case; I hit on someone at a party right in front of my primary. I haven't suffered a hiccup of drama or a twinge of jealousy to speak of and all evidence (including verbal confirmation) indicates that I've been managing my primary's feelings satisfactorily too.</bragging> Does this sort of thing appeal to you?

No.

But I do expect that if humans become immortal superbeings, then given enough time, most people currently in fairytale monogamous relationships will switch to poly. (Though when people are immortal superbeings, I also expect it to become common that they'll spend a very long time if necessary searching for an instance of fairytale monogamy to be their first relationship.)

I guess my philosophy is that fairytale monogamy is optimal for the young (say under 200 years or so), while poly and other non-traditional arrangements are the choice of the adult.