At clubs - it could be as quick as an hour. But clubs are like that - convenient meetings. If we have clicked with a couple we have always played on the first night.
If we meet them on the internet, however, that is a whole other can of worms... You have the e-mails back and forth, the picture(s) you have to send, the initial meeting, then maybe another meeting or two, and perhaps a sexual encounter. But that is so tough to tell. Largely because you just don't know where the other couple is.
What I have noticed is that people who don't go to clubs really want to get to know people first. That is a valid reason. In defense of clubbers though, many of us do tend to spend a lot of time talking and playing pool - but the beds are right upstairs and hell, we're all here
But that is us - if we meet a couple on-line, there is certainly no guarantee that they will move as quickly as we do, so we end up following their lead. Our experience has been that internet couples are into the second date before they are ready to discuss play. Which isn't a bad thing at all - we've met some neat friends this way, and have maintained that friendship even when we haven't wanted to play.
One thing that we have also experienced, though, are couples who are really into going out for dinner and then try to let the whole swinging issue die. It's as if they use sex as lure to make friends. That can be a little weird. We even had one couple where the wife seemed to have no idea that we were all meeting as a potential swinger connection.
Spoomonkey