A recent survey found that most of couples enjoy their amazing sex only four years and two months into their relationship. Sexologists wanted to explain why sex in long-term relationships becomes boring.

They observed that usually couples often enjoy the best sex over time, when they are more steady with their bodies and even with one another and are not afraid to propose new fantasies in bed. Of course couples can enjoy the best sex many years into a relationship and marriage.

It is not true that sex lives will take care of themselves, like everything else. So, you need to feed every part of your relationship, adding your sexual life.

So, how do you keep the passion flowing in a long-term relationship? The answer of this question can be only one. After four years sex becomes multivariate and that means not pointing on just the corporal aspect. Substantially it means being turned on mentally, emotionally and of course physically as we become more calm, relaxed with each other and our emotional connection is much powerful and stronger.

Unfortunately the road to lifelong passion is very rear a smooth and sweet one. While some couples never seem to get tired of each other, but other pairs seem to lose their sexual desires over the years. The main causes of a couple’s sex life are of course children and long, hard working days at the office.

"Don't get censure in a prototype or routine. Somewhat as simple as moving your sex place from the bedroom to the living room or having sex in the morning if you generally do it at night," said sexuality educator Ellen Friedrichs.

While you wouldn't want to refuse your partner to have sex, taking the time to do other things, like going to a museum, joining friends for dinner at a new restaurant - will excite your sex life.

Emotional intimacy is the main part of maintaining a strong sexual connection, declared marriage and family therapist Susan Scott Hennings of San Jose.

"At the beginning, games, sexual fantasies and sometimes risk are enough to make sex pleasure arouse. But after you have made love a few hundred times, it's your sensation of innocence, humor, adventure, and acceptance that will incite continued craving," added Hennings.

So, the best sex is when you feel free and relaxed with your partner.