When it comes to long-term relationships, most people have wondered (probably just to themselves), When will the sex get boring? Sure, this sounds like fodder for a cheesy sitcom plot, but the truth is, those early sexual sparks just don't always last. And now, a study from the Archives of Sexual Behavior has given you and your partner's best sex an expiration date: Basically, enjoy the hot-and-heavy first year while it lasts. The study authors asked almost 3,000 heterosexual participants between the ages of 25 and 41 to rank various time markers in their relationships (the first six months, the second and third years, etc.) based on how satisfying their sex was during that time. They found that sexual satisfaction peaked one year into these couples' relationships — and then began a steady decline. (Those are exact words from the study: "steady decline." Sigh.) The researchers also tested for potentially influential factors, and, surprisingly, it didn't matter whether or not a couple had kids; their quality of sex remained the same. What about conflict-heavy couples? Does emotional tension lead to fireworks in the bedroom? Nope: Couples who fought more reported less-satisfying sex. For those of you well past the one-year mark, don't despair — and keep the study's sample age range in mind. With the oldest participant clocking in at 41, we can't say for sure that even these folks won't hit a second, sexy stride in their 80s. If it happened for Hugh Hefner, it can happen for you.