"Giving up your job to support your husband and raise kids is fine - if nothing ever goes wrong."

When do you know a marriage is going to last? After 10, 20, 50 years?

The short answer is: you never know. People change, the world moves, life is heartbreakingly unfair and unbelievably magnanimous.

It was reported on the weekend that Channel 9 morning TV host Karl Stefanovic has separated from his wife of 21 years, Cassandra Thorburn, and is currently living in James Packer’s Bondi apartment.

They have three children together and Stefanovic has previously commented that he couldn’t have the successful career he has if his wife didn’t give up hers to raise their family.

“She gave up a promising career at the ABC and I’m forever thankful and tremendously appreciative of that,” he said last year.

“Cass wanted to be at home, and wants to be there now, and we’re very lucky to be in a financial position where we can do that. But should she ever want to go back to work, then of course she can.”

                                                                 Karl Stefanovic Image: Channel 9. 

As Stefanovic said last year, they are in a fortunate financial position — but most women, when there is a marriage split, need to work or go back to work. That's where the promises and sacrifices made by the partner who has stayed home to raise children and run the house decades before suddenly amount to nothing.

One out of five divorces today involve people who've been married for 20 years or more. There tends to be a lot of compromise, logic and sometimes, even hypocrisy, in relationships that long. The very thing you swore you would never do as a bright-eyed, ambitious, talented 22-year-old moves bit by bit to something you do after a 20 minute conversation 10 years later.

There's no way you will be the kind of person who brings stinky canned tuna to lunch for work. Then you do, because you've bought an apartment and buying lunch every day is expensive.

There's no way you would spend $1000 on a vacuum cleaner, or talk about a vacuum cleaner in public. Then you do, because a dirty floor becomes a particular kind of hell.

There's no way you would give up your job to be a full-time stay at home mum. Or maybe you would, but only when they are little - not for 15 or 20 years. Then you do, because it just makes sense for everyone in the family.

I have a friend who is divorcing from her husband of 21 years, too. She gave up work after their first child was born, they went on to have two more and she hasn't had a pay-check in around 15 years.

We went to university together. Then we started our first "proper" jobs together. She started a family and then I did. And that's where our paths diverted.

Lisa Wilkinson speaks to Mia Freedman about merging work and family life. (Post continues after audio.)

She had the means to give up work. "It makes sense at the moment," she kept telling me. Then it moved to, "Well, what would I do now?" I stayed working, part-time. There were so many years, over a decade in there, where I was secretly envious of her free time and her spontaneous ways.

Then her relationship fell apart and now she needs to get a job. But it's hard when you haven't worked for 15 years and the changes to the workforce in that time have been seismic. She left work around the time WIFI was released, but no one was using it because it didn't really work. Desk-top computers were bulbous and slow. Email was a toddler. iPhones weren't invented. The job she had doesn't really exist any more.

Everything is different; her skills and confidence included and despite trying she can't find a job. Not even one that basically requires the barest of abilities.

And, yes, we can all do that thing where we say, "look at her skills, she's run a household, she's effectively been a CEO, she's an Olympic multi-tasker". But she hasn't been a CEO and no employer really believes "mummy multi-tasking" can make up for 15 years in the workforce.

What they see is a women who has been unemployed for a very, very long time.

I know women who work full-time, part-time and not at all, and there are real costs associated with every configuration, but the harsh reality is working, in some capacity, after you become a mum gives you some kind of separation insurance. If your world changes and your partner leaves, or you leave them, you can provide for your family. You can pay at least some of the bills. If you work part-time you have a better chance of finding a full-time job if you need it.

Giving up work for you family is often a decision made out of love. It doesn't seem right to bring into the love equation the words financial security, loss of income and lack of superannuation next to Tommy, 2, Lucy, 6, and loving, devoted husband Ryan. But everyone grows up in a family. Sometimes they grow away too.

U.S. author Samantha Ettus is a 44-year-old mother of three and says she is already receiving hate mail for her book that is yet to hit shelves. The Pie Life: A Guilt-Free Recipe for Success and Satisfaction is billed as a self help book for women who work and Ettus is very clear that women who don't work are dissatisfied at their core.

“Where you see a woman who is not in an independent pursuit of her own life goals, you’ll likely find an anxious child, an over-perfected home, a marriage out of balance and a school administrator who wishes this woman would get a job,” Ettus says rather sensationally.

“Would you ever say someone who spends every moment at the office has a good and satisfying life? A woman who spends every moment doting on her family has an equally unbalanced life.”

A photo posted by Samantha Ettus (@samanthaettus) on Sep 15, 2016 at 9:40am PDT

Of course balance and fulfillment are important reasons for a woman to continue working after she has had children. But there is also another: the inability for anyone to predict the future.

If you asked me 15 years ago about my friend I would have told you I totally believe they will last the distance. They were in love, strong, together, beautiful to be around. And for the longest while, 21 years, they did last.

But what of the next 21 years, and even the 21 years after that for my friend? Those decades don't look so good if you have no control over your financial future, if you are stuck in a job that is killing you, if your self worth has plummeted, if you are looking at your ex flying high in the workforce and you can barely walk, if you have no power because you have no gold.

All the women I know who have given up their jobs to raise children, do what they feel is right for them and their family at the time. But time moves relentlessly forward, people change and that one decision can leave a woman who has always been the one to sacrifice, who has always been the centre of her home and family, a woman adrift and unwanted in the workforce. A woman with a very uncertain future. A woman who now has to rely financially on her ex. A woman plagued by self doubt. A woman whose contribution to the world by raising kids has been erased. A woman who has to start again right when she should be flying herself.

It doesn't seem fair. It doesn't seem right. But it is a reality.

I wonder if my friend would make the same choice again?