Heterosexual relationships, in my opinion of course, go through stages. My idea of such and how I have come to see it…
Dating sex – That first time your both together is very exciting. You both call each other a lot and can’t wait to see each other again and get naked. 
You leave little notes for each other in emails and hidden places.
Move in together sex– the next stage can sometimes be the deal breaker but if it works, it can be both funny and a learning experience. Sex gets better because your around each other more and can find other ways to engage in it and get creative. If you make it past here the next stage is obvious.
Marriage sex – They say the first year is the hardest. That’s only because of money and not being used to each others habits, and I can’t say for sure especially if you lived together first. But the sex is great. There’s also a saying. “Put one jelly bean in a jar for every time you have sex and at the end of the first year take one out for every time you have sex” In the end the jar never gets emptied. That’s gotta tell you something. Side note: You kiss everywhere and all the time. People tell you to get a room. Sound familiar?
Friends with Benefits sex – After you realize the jar is still more than half full and your 5 or 10 years into your marriage, you know something isn’t quite right. Your sex life turns into weekends, birthdays and anniversaries and maybe on vacations. The time between becomes longer and longer, so much that you can’t remember the last time. You don’t kiss like you used to. Just pecks hello and good bye.
Room-mates ( no) sex- when the sex finally stops you become not much more than room mates who on occasion have dinner together and watch television. You can tell when this starts to happen because the kissing will come to an end. Oh yeah a side note about television. Television is perhaps the worst thing for a marriage. Couples not only get complacent because all they do is watch sitcom and reality show night after night but its also a curse because there is more sex and nudity happening on prime time than in their own bedroom. Depressing to say the least. Life passes by without notice because the biggest thing you look froward to at night is the next episode of your favorite show.
Cheating Spouse ( sex anew) – At some point someone will cheat. At the very least someone will think about it and start finding ways to stay away from home. Usually someone at work catches your attention and you begin to like the way that person is with you. The sad part about this stage is your looking for those same feelings you had with your spouse. That spark,that makes everything in your life seems unimportant except being together.
Divorce – in the end you will wonder how you ever loved that person. You’ll either be very happy to get your freedom or sad because you failed at something that could have been saved. Either way its over.
“I am only a man. I can not read your mind. I can only make you “happier” but only if you are happy already. I can love only one woman but only if you let it be you. I can fix whats broken but I can’t fix what you don’t want repaired.”
Just one man’s opinion…
The Regular Guy