Originally Posted by SNeacail
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.
I agree completely. Don't "trap" yourself with mono thinking. After 25 years together in a mono relationship my wife and I had a very satisfying Poly relationship for about 5 years. It all boils down to communication.