In the stages of a relationship or marriage, there are four types of sex a couple generally has.
1) Backseat sex - You're so into one another that you just do it all the time. In the back seat of a car, in the kitchen, in the bathroom... wherever you can, you're just tearing into one another.
2) Bedroom sex - you're older, you're together, maybe you've got kids... so that means you're stuck having bedroom sex. Maybe you have a night of the week in which you're required to hump one another, you make appointments, and most importantly, you retreat into the bedroom for your lovemaking. It's not an adventure anymore, just a job.
3) Hallway sex - A little farther into the relationship, once you get into the double digits, your partner's little quirks stop being cute and start making you want to strangle him/her. Hallway sex is where, when you pass one another in the hallway and say, "Fuck you!"
4) Courtroom sex - This is the stage of the relationship in which your old lady takes you before the judge and her and her lawyers screw you in front of the whole court.