Originally Posted by Dave
On the other hand, we have good reason to believe that, once a mono relationship has gone past a certain point, and both sides have become used to mutual exclusivity, it is next to impossible to take those privileges away from each other again, without causing substantial damage to the relationship.
I don't believe this. Relationships cycle and as someone else here said, they are fluid. Enjoy each other, spend the time of exclusivity getting to know your partner and learning how to communicate effectively. If you are communicating and know that you can talk to your partner about everything, then it shouldn't come as a surprise when either of you find someone else that could be another potential interest. I would think that you would want to share your excitement over a new potential with your partner and have her share in your excitement or be able to pull you back when you aren't thinking rationally.