There is no set time frame for how long the honeymoon phase lasts in a relationship. It can last anywhere from a few months to a year or more. The honeymoon phase is a time when couples are typically very happy and in love with each other. They enjoy being around each other and are always looking for ways to please each other. As the honeymoon phase wears off, couples often start to experience some of the more difficult aspects of being in a relationship.