A bit late to the party on this thread...
I am part of a quad which has been together for almost a years now. It all started as best of friends (neighbors) for several years before we stumbled into this lifestyle completely be accident. Both couples are happily married with children for many years. We have had some ups and downs but we always work it out... it is truly a wonderful thing. Honest and open communication is the secret for us. We hang out with each other all the time, some week nights, weekends, holidays, family events, even events with our individual family and friends.
It's nice to connect with others in the same boat, esp with other people that are new to this lifestyle as well.