Have you ever told your partner that it would be OK to try Bi? Years ago I told my wife that I think 2 women together is Beautiful and extremely Sexy. Not missing a beat, she bounced it back to me.
Shit, actually sitting and watching two women do each other is so fucking erotic and can be humbling to see another woman taking your lady apart at the seams and in ways you couldn't imagine. With my first wife, I didn't have to convince her that it was okay to try it because she already was but tried to hide it from me and denying it when I'd tell her that, look, it's okay to be bi because I am. First time I saw her making love with a woman? I almost nutted on myself. But, for the other guys out there trying to get wifey to give him permission to try some dick - or trying to convince her that getting some pussy would be good for her... and so he can go get some dick to go with some pussy? A lot of guys aren't as lucky as topper and other guys - including myself - have been in this.
This can be a slippery slope for couples if not fully discussed. I had a close friend years ago that suggested it and was involved with FFM threesomes to find out 6 months later his wife wanted a divorce as she was in a relationship with that other woman.