According to experts, the honeymoon phase lasts only a maximum of 18 to 24 months...but it can end way sooner. It's different for every relationship.
That doesn't mean the end of the honeymoon phase is a bad thing. "It’s impossible to keep up that kind of level of impressing and going and doing and being involved in each other’s lives that you did during the honeymoon period," says Jane Greer, Marriage and Family Therapist and author of What About Me? Stop Selfishness from Ruining My Relationship. Your brain and body can't function off butterflies (a.k.a. adrenaline) forever—at some point, you need to come back down to neutral.