On the whole it was an incredibly great learning experience for me. Here are the things I've learned about myself and what I need when my Master has more-than-one relationship.
First, I am glad that Master and I have such a solid relationship. Poly never would have worked if I didn't feel safe and stable as his long-term partner. As it was, I did learn that equal treatment (or at least explained unequal treatment) was important, because I had moments where I realized that there was a gram or two of envy for something that he would do for her when he would't do the same for me.
Secondly, I learned that while poly-parenting works for some people, it doesn't work for me. Our little munchkins are one of my favorite things about our life together, and I am highly protective of them. I work hard to ensure their needs are met, that we indulge some of their wants, and give them the tools they're going to need as they get older. Master and I have parenting policies and approaches that have shown they work, and a sudden change suggested by poly-partner(s) could be incredibly disruptive (especially for our oldest) and challenging for me. Master and I trust each other's parenting practices; we don’t have that background with anyone else, and I don’t expect that foundation to exist in any future relationships while our kids still need parents. We know that sometimes here on the blog, and in real life, we’ll scathingly mention that they do impact how often we get to indulge in heavy play; but that does not accurately reflect how much we adore them or how much we devote to them.
Thirdly, while Master remains poly (probably by nature, considering genetic history), I no longer hold any desire in me for extra intimate relationships. Master has poked and prodded at this statement, trying to understand the depth and breadth of it. I like friends, friends are great, and I do hope that I can be friends with any future poly-partner(s) Master might find. But I'm not so inclined to have sex with anyone except Master these days. Perhaps the waning libido of perimenopause might be to blame, or the fact that my fear of being touched has reared its head again; but it feels deeper than that – it feels like a truth of my heart. He revs my engine; he understands my strengths, my vulnerabilities and my weaknesses. With him, I feel utterly his, and those moments are so sacred that I can't imagine sharing them with anyone. Maybe I've become semi-asexual outside my relationship with Master. Who knows?
Fourth, I feel pretty comfortable in the knowledge that poly-partner(s) relationships with Master aren't about me. Nothing about them is any of my business unless they want to share; it's none of my business how often they are intimate, when or where. Same goes for uploading and sharing of pictures -- it seems foolish to ask him for advance notice that he's going to be sharing stuff on FetLife -- and the perks of him sharing is I'll get a bit of perving in myself. ;) The only thing that's any of my business is knowing that if they are intimate they are adhering to the agreed upon safe-sex practices.
Lastly; time. Oh how important this fleeting thing can be. I've learned that I'm okay being by myself. It's okay when Master isn't with me all weekend or overnight. It's okay if he needs to spend an hour in a text message conversation, or take calls from his poly-partner(s). But I now know that if I have a hope for some time that will be solely for Master and I, I need to be able to clearly voice that. When I want time to spend with Master that's uninterrupted, it's something I need to make clear to everyone (because they have needs and requests too), and not just hope that I'll get a few hours where he isn't needing to engage in conversations with his poly-partner(s).
(TL;DR) I've learned that I can be okay while Master has other partners, that I can experience a fraction of jealousy and envy if I'm not talking about how I feel or what I need. I've learned that I learned how to communicate better with Master as his property. I've learned that I can still get frustrated and not know what I need to say to express myself to someone else...but that is something I think I can learn how to do.