We just constantly get newbies here who think polyamory is all about triads. (I blame our mass media.) The reality is, polyamory means you get to date or have relationships with multiple people, all of whom are aware of each other. This does not mean you start as a couple who seeks to share one other person ("adding a third").
The reality is, you and your partner are not a couple blob. You are individuals with unique tastes in partners. What happens if you start to date some hottie who is all excited to have sex with two beautiful women, only to find out he really prefers one of you over the other? Or one of you likes him, but the other loses interest?
Please read this article:
This article is a long, technical discussion of what being a "Unicorn Hunter" means, what's wrong with it, and how people in such a situation can try to avoid the negative stereotypes associated with such behavior and get the things that they are ultimately looking for. It is written in a…
davidlnoble.livejournal.com
And get a copy of the book
Opening Up, too.
Most formerly monoamorous couples are very entangled, and decide to do "polyamory" "together" for some reason, meaning they choose to not date separately and each find their own partners, but set their sights on finding one person who wants to be shared. In fact, most poly couples find that dating separately is much much easier and more guaranteed to be successful.
I am a woman in a long term poly nesting relationship with a woman, and we both have always sought our own bfs. I wouldn't want to have group sex all the time. My gf's libido is less strong than mine. So she'd probably take a pass on sex when the guy and I wanted to do it, lots of the time. That would be awkward.
Some people do parallel poly, where their partners never even meet each other, and that's fine, too.