This usually happens during the “what are we?” conversation when a dating situation turns into a relationship. Usually the woman will initiate this conversation. Sometimes, people just evolve into a relationship after dating for a while – don’t let this happen, or you won’t have ‘the talk’ and she’ll probably have default (monogamous) relationship expectations. Initiate the conversation yourself if you have to. This is when you come back to the idea of an open relationship.