I moved out when I was 20, it was hell with a shit job, rent/bills was about 70%-80% of my income, ate poorly, social life went down the toilet. Moved back in and saved money while I worked part time and went back to study. Moved out again around 25 and it was a lot better with stable employment.
I guess now I'm technically back, mother had a fucked up year developing Crohn's disease, having a heart attack, and a long term injury requiring her ankle joints to be fused. Father seriously messed up his shoulder requiring surgery (He's a builder, so fairly important) and lost around 30% strength in his dominant arm. Not in the same house though, they subdivided their block and built a 2nd house, so I rent that out relatively cheap while doing pretty much everything that involves physical effort (lawn, repairs, odd day off here and there working for my dad).
So from personal experience, whenever they're able to financially support themselves and can live in a way that won't compromise their physical/mental health. Had I not rushed to get out at 20, I could have probably moved out comfortably at 23-24.