I left the house at 17 & ever after only came to visit.
Down on my luck in the 1970’s & lived in a rooming house & later a garage apartment. Never considered living with Mom & Dad.
Then came the day “when a man shall leave his father & mother, and shall cleave unto his wife”. Decades of blessed life together since.
FWIW my Dad was in the infantry in WWII. Early twenties when the war ended. In old photos he & his fellow soldiers all look well into their thirties. Some were 18.
Same here, and I'm a woman. Luckily for my parents, their example of hard work and living within your means was not lost on me.