The three stages of marital sex are as follows:
Stage 1, House Sex: Upon first being married, the newlyweds engage in sex all over the house; living room, kitchen, shower, etc.
Stage 2, Bedroom Sex: After the "honeymoon phase" wears off, sex is only found in the bedroom.
Stage 3, Hallway Sex: Being married for so long, the only sex you get is passing each other in the hall and saying, "Fuck you".