Thanks for bringing up these questions, Qmoq.
I have wondered the same things. My Dom and I have talked about a possible addition, I feel it would add to what we have...so its good to hear what others have to say about their own experiences.

I am not the jealous type, I think I would find it easier to talk about what is best for everyone rather than to harbor negative feelings.

I imagine the Dom and sub would need to be very honest with each other before someone new would be introduced as well.