I am literally the same as the friend of the OP.
I am in my early 50's, I live in a little 2 bed cottage in the sticks, mortgage free, 5 minutes walk from miles of woodland, 10 minutes walk from the river, and I retired at 50. I had a busy, hectic, professional job for 30 years that was OK for the first 20 years but too much for the last 10.
I have 2 kids (both grown and left home now,) and worked through having them, and through the deaths of both parents, (and caring for them when they were ailing and frail.)
I had the opportunity to retire early and I did. At 50. I now have no kids at home, no parents to care for, and no job to go to. After 3 decades of work, career, stress, juggling, caring for kids, caring for older family members (me and DH cared for his parents too for several years til they died 10 years ago,) I am now free..... free as a bird! No job to go to, no mortgage, and no responsibilities.
I have never been happier. I am still in good health, and I spend my days doing jigsaws and crossword puzzles, reading, working on the novel I have been meaning to write for 20 years, cycling, swimming, walking round the woodlands and river bank, meeting adult DC for lunch once a week, meeting close friends for lunch, joining in with the odd village event, and bingeing on netflix programmes, whilst knocking back a couple of glasses of wine.
I know some women my age (or within 3 years of it,) who work, some in jobs they hate, but all in jobs that are hectic, and they really genuinely envy me. Some flat out admit it, and some don't admit it, but make spiteful, catty remarks about how they 'can't understand how I can just not work. and surely I must get bored!
I never ever get bored, and can quite easily 'not work' thanks. I've paid my dues and earned my stripes. It's my time now. DH is retiring in 2 years. (At 55.) Then we will go on a world cruise. The one woman I know is so bitter and jealous, that she will probably have a meltdown when I tell her we're going on a world cruise.
But yep, you could not pay me enough now to return to work. And I genuinely feel sorry for people who still have many years of it left.
Oh, and I had 2 kids (in my mid 20's) and it didn't age me. I don't look any older than my age. In fact, on a good day, I look 5-7 years younger. Maybe it's because I was quite young-ish when I had them. I know a woman who had no kids and is 3 years younger than me, and she looks older than me. So it doesn't always follow that kids age you.
I have to say my life IS stress-free and has been for several years. (Since I finished work!)
It could change again in the future at some time, but right now, life is amazing.