I think that level of condescension is uncalled-for.
Answer the question. What
is your experience with polyamory? I agree with AT that some of your advice has been unhelpful, and at times even downright harmful. It's not unfair to question your experience if you're giving advice that is contrary to the experience of people who have been living polyamorously for years, sometimes decades.
Furthermore, there are many inconsistencies in your posts. This might feel like an attack on you, but I am genuinely concerned about your competence to provide useful advice on this forum, and the potential damage that can come from that.
Let's start with basic facts. You are at once 20, 28, and 30-something.
There are no others in our relationship and don’t contemplate any, except that we agree to have ex’s or old friends privileges with the consensus of the others.
soon to be married to C, a 24 y/o bisexual polyamorous woman.
By your own admission, you are living a "conventional lifestyle" that suggests inexperience with polyamory. You are in a relationship with a polyamorous woman, but you don't contemplate having others in your relationship except an agreement to sleep with exes and friends. Not only is that unconventional, but it makes me wonder whether she is suppressing her polyamory for your sake.
You're in the place a lot of couples are who realize they need another person in their relationship.
From what experience do you make this generalization? No couple ever "needs" another person in their relationship. If they feel like they do, then they have some serious relationship issues to solve first. It's a bad idea to throw a third person into a relationship that "needs" anything it doesn't already have. Again, this suggests inexperience with polyamory.
An honest conversation is a must with every involved, except maybe current bf is he's soon to be out of the picture.
Suggesting that a person lie to their partner is harmful. It's what first raised my fur about you, and I'm not yet convinced that you've learned your lesson.
Have you slept with either of the couple? I think that would be a requisite before you begin.
When the time comes that you meet someone you feel attracted to and want to have sex with, that's the time to exercise your option of having another relationship in your life.
This suggest a fundamental misunderstanding of polyamory, where the focus is not about sex, but rather love and committed romantic relationships.
You almost seem to understand that here:
Remember the -amory part. It's about love and welcoming another person into your marriage, not about fucking around.
But then you fall into the classic newbie-poly blunder about "welcoming another person into your marriage" which is unrealistic. Anyone with experience will tell you it usually doesn't work out that way. Furthermore, you said this as though you'd just read it in someone's tagline.
You know already that he could have already moved on to another person and he's not so much polyamorous as polysexual.
Could be you need to split up for a while and sort things out.
To me, her situation sounded more like NRE, with the added complication of time constrictions in both their schedules. Nothing in her post suggests that the primary basis of his relationship with the other woman is sexual. You're pretty much urging her to break up with him. That's not constructive or helpful.
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What I've summarized here are some examples of poor judgement and potentially harmful advice. Not everything you've said has been negative, so I'm sure you can learn from your mistakes. However, AutumnalTone is correct that until you can demonstrate more experience with polyamory, or at least a better understanding of what's been shared on this forum by people who have that experience, it would be best if you stop giving advice to other people and instead focus on yourself.