Was reading this with interest because I have come across some women that are one and done and perhaps this explains why. When I was younger I used to hold off cumming as long as I could because that was exactly how I'd feel after I came. I was capable of more general physical activity after I came, I just didn't want any more sex at that moment.
Not sure if women can do this but I know that guys can consciously hold back. If the woman is on top then perhaps she can control the pace and slow things down if she feels she's going over the edge? If so, then things could start with you on top and you could extend things out that way.
We play with condoms when playing with others so that tends to slow down most guys due to some minimal desensitization. As I believe Rabbit (or is it Ratchet now...lol) suggested you can look into some desensitizing creams/gels. As weird as this may seem, some of the ones that are supposed to increase sensitivity (warming/cooling gels) work the opposite for us as we find them distracting, so may be worth a try.
Of course the beauty of swinging is that each or both of you can have multiple partners. Some days the Mrs is more insatiable than me and vice versa, and at parties we're both welcome to play till contented. Kind of one of the big reasons for being in the LS, for us anyway.
One last thing is that other partners may not be able to get you off like your mate. I know that no other woman can make me orgasm like the Mrs and it is the same for her with me. It's one of the reasons the LS works so well for us.

