I'm 46, my wife is 36. Kids are 6 and 1. We can FIRE in 3-4 years.
Currently we live on $30k, put $60k on mortgage, and pay $30k in taxes. With 180k left on mortgage, that's 3 years, or 4 years if other weird expenses come up, one of us becomes unemployed, or whatever.
We get $20k in income from a rental property. So after mortgage, we just need $10k income from something else. Unemployment benefit in Australia is $12.5k, and minimum full-time wage $36k, so $10k isn't asking much.
Now, if we want to live it up, or spend more on kids' education or something, that's another matter. But currently I'm a stay-at-home father and work part-time doing something I love, I don't see any reason to change that in the next 10 years or so. And I certainly don't see my wife sitting around at home doing nothing.