Think your marriage is beyond the help of Valentines? Sex life flagging? Just wait. The sex should get better after 15 years, at least if you’re a woman. That’s one of the revelations of a recent study from the Kinsey Institute at Indiana University, which looked at the intimacy and sex lives of more than 1,000 couples who were together an average 25 years. What really matters in a relationship? That depends on who you ask: men or women. An Indiana University news release reports that for men, relationship happiness was more likely if the man was in good health and if his partner experienced orgasm. Frequent kissing or cuddling also predicted happiness in the relationship for men, but not for women. And while men said they grew happier in their relationships over the years, the women reported a rise in their sexual satisfaction over the same period. Women who had been with their partner for less than 15 years were less likely to report sexual satisfaction, but after 15 years, the percentage went up significantly. Wait, there’s more: compared with the U.S. men, Japanese men reported significantly (2.61 times) more sexual satisfaction in their relationships. For women, Japanese and Brazilian women were more likely to report being satisfied sexually than Americans.