Last July, Newsweek magazine declared that 2009 was the "Year of the Cougar". They also speculated that the trend would be extinct by the end of the year. So far it shows no signs of waning.
Neither does the disparaging tag. Why women who date younger men have been branded with the name of a predatory animal is anyone's guess. Marketeers have hijacked the trend with cougar cruises, dating sites and a library of dating manuals, while the film and TV industry has capitalised on it with shows like Cougar Town and films like Cheri.
Despite the headlines, though, older women/younger men relationships have hardly exploded in the dating scene. It's a trend born and raised in Hollywood, with Madonna and Demi Moore as the reluctant poster girls.
Perhaps that's why we feel we can say "it will never last" with authority when we hear about the latest older woman/younger man pairing. There's no doubt that these relationships can be successful, but the big question is whether or not they are enduring.
There was an age gap of nine years between the now estranged John Mayer and Jennifer Aniston. Tellingly, he said afterwards: "Have you ever loved somebody, loved her completely, but had to end the relationship for life reasons?"
Eight years separated Kelly Brook and Danny Cipriani, who split after two years. Like Mayer, Cipriani was later linked to a younger woman.
There was nine years between Cameron Diaz and Justin Timberlake. "It's not like this is the first time in the history of human relationships that people were drawn to one another because of who they are, not what age they are," Diaz said at the time. They split after almost four years together and he soon moved on to Jessica Biel, who is one year younger than him.
"There were, like, just pheromones flying off the walls," said Halle Berry about meeting model Gabriel Aubry, nine years her junior, for the first time. Alas, chemical attraction only goes so far -- they split five years later.
Examples abound. Sadie Frost is five years older than her ex-husband Jude Law. He is now dating Sienna Miller, nine years his junior.
Kim Cattrall, who plays Samantha in Sex and the City, recently split from chef Alan Wyse, 22 years her junior. Alan's father, Carl, revealed that they separated because Alan refused to be a kept man. "He's a grown man. He needs his independence -- to stand on his own two feet."
Cattrall is a vocal opponent to the use of the word 'cougar' and once refused to appear on a magazine cover when the editor asked her to pose alongside an actual cougar.
On the contrary, Susan Sarandon, who recently split from Tim Robbins, 12 years her junior, says she loves the tag. "I don't get why old people would mind being called a cougar. Cougars are hot, sexy and mature. What would they rather be called? 'Dignified'? Who wants that? No one wants to hang out with someone 'dignified'."
Since the split, the 63-year-old has been linked to a 31-year-old toyboy.
Do we anticipate the worst for these relationships because they defy natural order? Put simply, an older man and a younger woman promotes survival of the species; an older woman and younger man does not. A study by Gothenburg University and Oxford University studied 400 lonely hearts ads to see how people choose partners.
Predictably, men in all categories preferred younger partners. Of a total of 97 men who mentioned age in their ads, only three were looking for an older partner. Younger women preferred older men. However, the majority of women over 60 were looking for a younger man.
Perhaps it hinges on fertility. Remember, a woman's fertility has a deadline, a man's does not. For many age-gap relationships, the inability to have children can become a concern.
"I don't think we've evolved that much that we can depart completely from that," says Lisa O'Hara, a relationship counsellor with Marriage and Relationship Counselling Services (MRCS). "Departing from the way nature intended us to be can be very confusing."
"Not every woman wants to have a child and not every man wants to have a child either," says Allison Keating, a psychologist at the bWell Clinic. "It's about knowing what both people want."
As with any age-gap relationship, it's about being aware of the potential difficulties. Often the couple can suffer from anxiety when it comes to introducing their partner to friends and family . . . or acute embarrassment when said partner is thought to be their son.
"I worked with a couple where an age-gap existed and they were reluctant to introduce each other to friends and family for fear of being judged," explains O'Hara.
Age-gap couples also have to contend with personal insecurities when the ageing process begins to take its toll on one of them. "The person may think, 'I'm in my prime now but in a few years' time I'll be older and maybe they won't fancy me'," adds O'Hara. "They could become insecure."
Demi Moore (47) married to Ashton Kutcher (32) and taking pictures of herself in a bikini and posting them on Twitter is a perfect example.
"Some couples may find it difficult to relate to each other because of the generation gap," says O'Hara. "We bond by what we have in common."
Consider the photos of Jesus Luz and Madonna in Rio de Janeiro nightclub, Circus. While 23-year-old Luz danced topless, an exhausted- looking Madonna, 28 years his senior, sat it out.
Some say that age-gap relationships have a higher chance of infidelity. According to relationship expert, Ruth Houston, infidelity is more likely in relationships where there is an age difference of 15 to 20 years. She attributes this to the disparity in the sex drives of the two people involved.
Her theory holds for actors Francesca Annis and Ralph Fiennes who had 18 years between them. Their relationship came to an end when Fiennes had an affair with a 31-year-old woman.
Perhaps the last word should go to Joan Collins who is happily married to Percy Gibson, 32 years her junior. When a journalist questioned the age gap, she quipped: "If he dies, he dies."