May-December relationships are certainly common. About 8% of all married heterosexual couples have an age gap of ten years or more (there is very little data available for same-sex couples). Most of these are the cliche — an older man with a younger woman. About 1% involve an older woman with a younger man. But do they ever work?

The short answer is: at first. Men who are married to younger wives report high levels of relationship satisfaction — on par with those with no age difference – ditto wives with younger husbands. You can practically see the sparks flying in these matches. They bring out the best in each other. The younger mate makes them feel so alive, so energetic. The older spouse makes the younger feel so secure and adored. They're going bungee jumping this weekend and flying to Paris the next. Couples with significant age differences report greater trust and commitment and lower jealousy than similar-age couples.

Over time, however, the relationship happiness takes a nosedive.

"The people who are married to a much older or younger spouse tend to have larger declines in marital satisfaction over time compared to those who are married to spouses who are similar in age," Terra McKinnish, economics professor at the University of Colorado and co-author to a study published in Journal of Population Economicssaid.

Both men and women married to significantly older spouses are markedly less satisfied.

Other studies have found comparable results. "The larger the age gap between you and your partner, the more likely your marriage will end in divorce," Randy Olson, a senior data scientist at the University of Pennsylvania told AARP. "Only being one to five years away from your partner is nothing to worry about, but if you're old enough to be your partner's parent, then your marriage might be in trouble."

But is this necessarily a death knell?

"I have seen couples with significant age differences bridge that gap," relationship expert Rachel A. Sussman, LCSW, toldInsider. "They have to have a sense of humor and be comfortable discussing the pitfalls. I also think it works well when the younger partner is very mature for his/her age, and the older partner is playful and perhaps a bit immature."

Hear that? A sense of humor, ability to communicate? Age is not the sole predictor of relationship satisfaction. No one single factor spells doom in a relationship. Happiness between two people depends on a constellation of factors, including listening, fighting fair, and making time to foster physical and emotional intimacy, reports Psychology Today. There's also similarity. If you're ten years apart in age but both love reading mystery novels, taking long road trips, and going to bed early, you could be golden together forever.

One obstacle couples with a significant age difference may face is a social stigma. Research from Oakland University finds people often have strong, negative reactions to age-gap relationships because they assume there's an aspect of exploitation in the relationship, an exchange-based partnership (e.g., sex for a certain lifestyle) rather than a care-based partnership.

But having to overcome such an obstacle together as a team could strengthen a couple since one of the aspects of a happy partnership is working as a team.

"It is not a lack of love," wrote Friedrich Nietzsche, "but a lack of friendship that makes unhappy marriages." And a good friendship can span any age gap.