The never-ending teenage years now have an unofficial end date, thanks to an unexpected twist in the federal budget.

It’s 31, the age at which children must formally flee the parental healthcare nest by taking out their own health insurance.

Certainly, it’s a big gift to the health insurance industry, which is ailing.

The exodus of young people leaving private health has meant the ‘‘risk pool’’ of those insured is exacerbated because older people are likely to be less healthy than young people.

We’ve seen the effect of that in premiums, which are also increasing to keep up with the rising costs of medical procedures.

And all that has created a spiral, where young people are pulling the plug on private health.

Australian children and young adults have another reason to stay tight with their parents.

That’s the reason Scott Morrison has given the private health insurance industry a budget boost.

Fewer young people will make that decision now, at 24, to independently join a fund.

They’ll keep their private health status, courtesy of their ageing parents.

But this higher age of dependency raises a broader question, and that is how long our children will be reliant or semi-reliant on their parents.

This is coming to matter more and more. Ironically, while children are maturing mentally and physically at a younger age, they’re spending longer getting to an age of responsibility.

Social demographer Mark McCrindle calls our young teens ‘up-agers’, because social media has meant they are now ‘older’ at an earlier stage.

And economic circumstance and study and a range of other factors has meant they remain reliant, much later than their parents, and well into their 20s.

The later age at which young people now marry or join committed long-term relationships also plays a role here.

Look around at your friends and colleagues, and most 50-somethings will have adult children coming and going; sometimes because it suits them, and other times because the jobs market or rental prices or study dictates the need for it.

COVID has magnified this trend, and the social implications of it for parents, as well as children – from cooking dinner to paying expenses to defer decisions to downsize – are only beginning to play out.

Prime Minister Scott Morrison and Treasurer Josh Frydenberg after the budget. Photo: AAP

But back to health, and the implications of allowing a 31-year-old dependent to remain on their parents’ health policy.

Will the fact children are on health benefits for longer push up premiums? After all, some of those on mum and dad’s healthcare scheme will be having children while dependent on their parents.

What’s next? The grandchildren should be in the scheme too (at least until their parents turn 31). What about spouses or co-habitants?

And how does this extend to other areas? At what age will children be deemed independent and eligible for other social benefits without being means-tested on their parents’ income?

Behind all this is the generational equity issue.

Baby boomers have benefited from a rare series of events that have allowed them to build wealth through property and shares and super.

The high-single-digit returns of super in the past decade are unlikely to be matched over the next decade.

So should we expect parents to be transferring some of that wealth to either fund housing, health care, or grandchild care?

Scott Morrison’s decision might have been a gift for young people but it raises more questions that need answers, including this one: If children are dependent on their parents for health care until age 31, does that mean they will wash the dishes, put out the rubbish and oil the wheelchair?