A new study reveals which attitudes lead to the greatest satisfaction.

There’s no great mystery in understanding why couples become less sexually active as their relationship matures: As passionate love mellows into a relationship characterized by intimacy and companionship, long-term couples will almost certainly have sex less frequently. The demands of daily life and the reality of taking care of a household mean that many couples devote less time exclusively to their physical relationship.

But it's an issue worth addressing: We may prefer not to think about our parents or grandparents having sex, but plenty of older couples maintain physical intimacy in their later years. There are real benefits in continuing sexual activity throughout life, as shown by researchers studying sexual life expectancy. If for no other reason than to support your long-term mental and physical well-being, figuring out the formula for staying sexually active with your long-term partner is a good idea.

To answer the question of what keeps the sexual spark alive in long-term relationships, University of Toronto psychologist Amy Muise and her collaborators (2013) studied 44 couples who were in relationships lasting from 3 to 39 years. On average, these couples had been together approximately 11 years. All were living together; about two-thirds were married; and about half had children. These couples, then, represented a range of length and types of relationship and family status.

Unlike so many studies on relationships that involve undergraduates completing questionnaires over the course of an hour or so for experimental credit, the participants in this study answered questions 10 minutes each night for three weeks. They were paid a modest amount ($40), and about three-quarters of them also responded to a follow-up survey about four months after completing the daily ratings.

Finding out what works

Maintaining strong sexual connections, Muise and her team argued, requires that each partner in the couple put the other partner’s needs first. Like the impoverished couple in O’Henry’s "Gift of the Magi," a partner in a successful long-term relationship is willing to sacrifice what he or she needs to be happy in order to please the other person. Rather than foreshadowing a woeful ending, however, the self-sacrificing made within happy couples should bring joy to both partners. This view of relationships, known as the communal model, contrasts with the exchange model, in which Partner A weighs his or her own contributions against those of Partner B. Couples strong on exchange motivation only help partners who will help them in turn.

In a relationship characterized by high communal strength, for example, you would be willing to give up the convenience of a relatively short commute to work if by moving a bit further away, your partner would also have a shorter distance to travel. In the exchange relationship, you’d only make this sacrifice if your partner would agree to some other condition, such as contributing more to household chores or helping out more with child care.

If you’re a communal type of person, the benefits of a relationship premised on this model would seem obvious. Your partner’s happiness becomes more important than your own, and there’s an inner satisfaction and even delight that you get out of giving. Making the logical jump to the sexual domain of your relationship, wanting to please your partner can be more of a turn-on than expecting your partner to reciprocate your every sensual gesture.

There’s more to long-lasting sex than wanting to please your partner, however. Muise and her team believed that scoring high on approach motivation would also benefit your long-term satisfaction in the bedroom. In high approach motivation, you look to sex for the pleasures it provides, either to yourself or your partner. Why else would someone want to have sex, you might ask? Consider, for example, situations in which sex primarily provides a distraction from problems. In avoidance motivation, partners regard sex significantly as a form of stress reduction or escapism.  

Putting these two dimensions together, Muise and team believed that couples high in both communal and approach motivation would have sexual relationships that would most likely withstand the test of time. In their study, they measured communal relationship strength with questions such as, “How large a cost would you incur to meet a need of your partner?” and communal sexual strength by asking, for example, “How high a priority for you is meeting the sexual needs of your partner?”

In their daily rating questions, participants reported whether or not they had had sex that day, and each time, they were to indicate whether it was to enhance their (or their partner’s) pleasure (approach) or if it was to avoid feeling upset, either for themselves or their partners (avoidance). The participants also provided overall ratings of their relationship happiness, sexual desire, and preference for alternative relationships. On average, participants reported having sexual activity once a week, with a range of once per day to once every 10 days.

By following their participants over the 3-week period (plus the four-month follow-up), Muise and her collaborators were able to track the connection between sexual motivation, desire, and relationship satisfaction. As they expected, the partners with higher levels of sexual communal strength (and not just general communal strength) had higher levels of sexual desire, especially if they were also higher in approach motivation. These findings persisted over time—the higher the communal/approach motivation, the less decline couples showed in relationship satisfaction.

Bringing It Home

There is a clear take-home message in this research: Using sex in exchange for other favors reaps few rewards in a long-term relationship. You also will find diminishing returns from using sex as a way to escape either your problems, your partner's problems, or those that plague you as a couple in general.  

You don’t have to be a complete pushover and never expect your partner to satisfy your needs to have a sexually intimate relationship that withstands the test of time. On the other hand, this study shows us that it’s important not to keep a relationship scorecard, especially in the bedroom. Be willing to give more than you receive, and it’s possible that both of you will experience sexual happiness for many years to come.