Just to add on to HopefulDad is that most BPD people have no boundaries they will do anything to please the person they are with, most will have sex and that's all it is, not "making love" just sex. What they do for you they will easily do for others. It has no sentimental value to them.
I agree with this in part, but also have a slightly different perspective. As so many others have described their relationships with a BPDex, mine was full of intense emotional highs and lows and over time the build-up of unresolved emotion became a constantly simmering volcano. And all the emotional tension we couldn't resolve through open communication, we would work out (or feel like we were working out) sexually. As Dontknow says, there were no physical boundaries. It was as if we were compensating for all the communication boundaries -- all the walls that were growing up between us when we tried to talk to one another -- by completely dropping our physical boundaries. There was an intensity and, by the end, even a kind of desperate longing in the way we made love. We were trying to reach out and feel each other physically because we couldn't get there any other way, by the end. And, yes, nothing was off-limits in terms of the sex acts we went for.
I have no doubt the sex involved intense emotions for my ex as well. The thing is, like so many other exes described here, she seemed to have no core emotional stability. So we could recreate those feelings of love and closeness while having sex, but that doesn't do anything to stabilise the relationship in the long term. Or even for the rest of the day. She would soon start raging at me again and playing mind games over jealousy and infidelity. And in this sense, my experience fits with what Dontknow says -- my ex would show me that she was ready/threatening to do for others what she would do for me ... .by the end she was always hinting at cheating. And that just became something I could not accept any more.
My ex is promiscuous, as she acknowledged herself. But I don't think it's because sex lacks an intense emotional side for her. Just the opposite. She uses sex either to connect or to play mind games or to punish or whatever. If anything, sex is emotionally overloaded for her.
Anyway, enough about her. How has this affected me post-breakup? It's definitely left an association in my mind between intense/passionate/wild/kinky sex, on the one hand, and an emotionally unstable relationship with communication barriers, on the other. This association does bother me, because right now I have trouble picturing truly great sex as part of a healthy relationship, where my partner and I are open with one another and aren't emotionally raw.
I'm grateful to have reached a point in my post-breakup recovery where I genuinely place much greater value on having a happy, stable, open relationship grounded in mutual trust and respect than on having those incredibly intense feelings of love and longing and a wild sex life. But I'd certainly be lying if I said I don't miss the sexual connection I had with my ex. I think, as others have noted, in a stable long-term relationship, you have to go about building that sexual chemistry differently. You have time to open up to one another about what you like. You don't have to worry about impressing one another with how wild and kinky you can be, because your relationship isn't grounded in a sexual connection. It takes a lot of pressure off of sex, which can also mean it takes away some of the thrill and excitement.
That said, what kind of relationship are you looking for? If you want a committed, monogamous, long-term relationship, it may be unrealistic to expect uninterrupted sexual intensity and bliss. True, it's nice to have that at the beginning of the relationship, at least. But if you've found someone you want to be with for other reasons, someone you see yourself with for the long-term, then I don't really buy this idea of a partner not being "all that good". She/he may be inexperienced or not know what they want. They might never have felt intimate enough with someone to let themselves go, or might not have that wild side your BPDex had where they don't need emotional intimacy to let go sexually. But if you're in a committed, long-term relationship, you have time to build that chemistry. You just have to be (or become) comfortable talking to one another about it, figuring out what excites each of you. Barring unusual circumstances, any couple that is open and comfortable together can build a good sex life.
That said, I can certainly relate to the longing for the completely uninhibited sex that was part of a past BPD relationship. I do miss it. A lot sometimes. And it has messed with my head in the way I describe above. But I don't mind trying something different. Life is full of surprises -- maybe trying to build sexual intimacy within a relationship that is built on trust and real emotional intimacy as well ... .could turn out to be its own kind of kinky. I think it helps not to take ourselves or our desires too seriously. Easier said than done when those desires weigh on us heavily.