That in particular is, and hasn't been something that happened. But you know, if either of us want something the other isn't so willing to do, we both understand. Not such a big deal for us - though I do understand where it would be a line for other folks. And that's OK, the main point is to be open about this sort of thing and be able to discuss it without fear of the other being angry. Yes, this has been discussed in my household, more in the theoretical sense because we both have some hesitations about the other person not wanting to be involved or worse, forced by a third, unknown party... even where it is legal. My own main reasoning for wanting such a thing is because I'm bisexual, and there are lots more men available for me than women. Folks have urges and get stuff stuck in their head, after all. Being able to share these thoughts is pretty great.
The rest of it is pretty normal stuff (watching porn, being physically attracted to others), though it is stuff folks tend to not discuss openly.