Married couples, de facto couples - couples of all kinds - complain that their love lives become less satisfying the longer they are together.

So I was interested to hear about a new trend apparently taking hold in the country's major capital cities. Mistress-keeping. Not just affair-having - random, clandestine relationships carried out by people who are supposed to be committed elsewhere - but something else, something more formal.

Mistress-keeping, something that has been commonplace in cultures around the world, throughout history, and is now, apparently, taking hold in modern-day Australia in a major way.

What is it exactly? Well, cast your mind through history and consider the concubine. A fixture of the French court - and many other courts besides - these were women who were professional lovers. More than lowly, street-shlepping prostitutes who operated in a sort of fast-food market of immediate satisfaction, these women were deliberate in their approach to trade, and had long-term rewards in mind. Like great artists, who exchanged their talents for the time and cash of a benevolent patron, these women swapped their company and corporeality for a place in society, a place to live, and piece of their keeper's financial pie.

And, according to reports going to back to 2012, the practice is alive and well. Websites such as like SeekingArrangement.com facilitate the process, connecting young women with men aged up to 70 years old for the purpose of a mutually satisfying mistress-master relationship. A news article from last year details this "sugar daddy, sugar baby" arrangement: young women sign up for an account, older men browse through the profiles, and when two parties meet, negotiations are carried out to determine the boundaries of these relationships.

Sex, however, isn't always on the cards, says the owner of the American-based company in an ABC story this year.

While talking about the rising numbers of Australian university students signing up to find rich benefactors, he says the ensuing exchanges aren't necessarily characterised by prostitution per se - unless those terms are negotiated by the two involved.

And presumably, they are. Indeed, as the story goes on to detail the amount of money these Sugar Daddies lavish on their younger babies, nominally to pay for their rising university fees, it's hard to imagine that there isn't some sort of sexual return. I'm sure I'm not alone in thinking that an older rich man seeking a younger, relatively poor woman for good times and company wouldn't do so unless a good-time-company shag was a given.

Aren't these women just a modern day version of mistresses of old? Aren't they the 21st century Australian equivalent of the concubine? A social standing so ancient, the Greeks permitted permitting the murder of a man should another have proof the scoundrel interfered with his kept woman?

"Of course it is," one woman tells me - a woman very connected to the business elite of Brisbane and Sydney. "Especially you see it with young female students who are coming to study here from overseas. Asian girls, European girls - it's a part of their culture there, it's a growing part of our culture here."

She's certainly right in one respect. There's been much written in recent years of China's Enlai - second wife second wives. An ancient role with new meaning today - young women, kept as status symbol by often shady Chinese businessmen, who know their worth, and seek to exploit it while their youthful stocks are high. One commentator describes them as the "direct product of China's current period of 'primitive accumulation,' or early-stage capitalism, in which economic changes are dramatically transforming social and sexual relationships."

Interesting. Especially when you consider that, here, and elsewhere, it's the economy, stupid, that sets the terms of our society. Everything is a trade, everything is an exchange, everything, it seems, is valued, not merely considered. If a husband is not getting from his wife what he expects is his part of their "bargain", is he then entitled to find it elsewhere? And, if a wife isn't keen on doing her part of their deal, should she begrudge a husband cashing in elsewhere?

"No - not when she gets to keep the house, the kids, the lifestyle," my elite-whisperer says. "What I'm seeing is that transaction - she gets her life as a wife paid for, he gets his husband status upheld, and he gets his satisfaction while another woman gets hers too.

"What's the problem?"

Well, what is the problem? If everyone's complicit, is there any reason for concern? Is an organised, recognised relationship with a mistress so bad for a couple who have found other reasons to stay together (kids, a house, a standing in society, etc)? Is it less offensive than a secret affair with someone else, built on dissatisfaction, but defined by the lack of courage to leave?

I, personally, wouldn't be with my husband unless we were only for each other. But my way isn't the only way - and it's certainly not right for everyone because it's right for me. What do you think?

Mistress-keeping - an ancient right, or a modern wrong?

Katherine Feeney is a journalist with the Nine Network Australia.

@katherinefeeney