I don’t think there is an age. Look at Tavi Gevinson, she’s probably one of the most influential young women on the internet who preaches a life of individualism. But then, we also have 50 year old housewives getting plastic surgery to look like women who are younger.
I think it comes when you grow internally. You realize you are what you are, and you have what you have. You can make yourself happy at the end of the day, that’s it. If you continually try and meet the standards of others you exhaust yourself. Then you aren’t getting anywhere.