Three isn't a crowd right?

Hey, everyone i am a happily married woman of 7 years (8 come august 1st) and two nights ago I finally confessed to him that I wanted an open marriage. By this I explained that I wanted another female to join us in our happiness. To my surprise he felt the same way. Of course as we have the same taste, we both wanted the same female. We messaged and she is agreeable. What I'm worried about is if there are any success stories with long lasting relationships between the three.