I don't have an answer for you, but I wanted to point out that you've skipped over a third way people come to poly -- single folks who decide to give it a go. Not everyone is coupled as the default! I had had some mono and some poly experiences as a teen and in my early twenties, none of which lasted. Then, as a person who had a couple of casual things going but was unpartnered, I started dating my gf. Since she was married, I was now in a poly relationship. Down the line, I started dating my bf as well. So, yeah, I don't fit the paradigm above, and I know many other people don't either.
If my gf and I break up and I dont seek another partner, since my bf isn't dating anyone else either, am I now done with my poly "phase"? Or am I just entering a mono "phase" which is bound to be temporary?
It's a bit.more complicated than the way you've presented it, is what I'm saying.
The major players. Me, 30ish bi female. Gia, girlfriend of 4+ years. Clay, boyfriend/dom. Davis, ex/friend/"it's complicated." Eddie, roommate & fwb.
The supporting cast. Eric, Gia's husband. Bee, Gia and Eric's toddler. Dexter, Gia's lover. Helen, Eric's lover. Izzy and Nikki, Clay's partners. Liam, Eddie's husband.