Wife got us into the lifestyle in our mid-twenties - full swap with other married couples. Wife also gave me a surprised fmf threesome for my 30th birthday. You may think that would be every guy's dream but stop and think a minute -- you got twice the work and you better hit two homeruns.
We were in the lifestyle for 20 years and had great times with few disappointments and we had the same rule about kissing. When we gave our vows the kissing the bride is putting the seal on the both of us. It is like you can borrow her for a night but I know who she's going home with. This rules leaves at least one thing that is special just between me and my wife.