Wife might try 3-some

Hello, I'm new to even thinking about my wife being penetrated by someone eles but for some reason I deeply, no punn intended, desire a cuckold lifestyle in my marriage. The problem: I am reasonably well endowed 8" and have wonderful stamena-she has no trouble reaching climax several times before I finish. When ever I try to mention another guy she seems indifferent to them as if shes fully satisfied?? The good news she said she would try a 3-some, how can I change my stars???