Nostalgic Adolescence

I had cause today to revisit a piece of favorite childhood literature from pre-Civil War-era America, c. "the flowering of New England."

Have you ever wanted to curl up, dormouse-like, in 1850?

Adolescence begins when one wakes up one day and realizes that there is nothing magic about adults: they are just children play-acting -some better than others- at being civilized, kind, and responsible. And a moment later, one realizes that there is nothing to stop one from similarly putting on the show of being civilized, kind, and responsible (or anything else). And when the play-acting becomes second nature, one has Arrived as an adult.
This is popularly understood to be true of social norms; my understanding is that it is also true of character.

I wonder whether it would be possible to play-act at being an early Victorian until it would become one's second nature, so that just as one walks around in a bubble of civility, kindness, and responsibility in a sometimes adult and sometimes childish world, one could walk around in a bubble of the borrowed memories of 1850 in a world that pulses with the Irritating Dissonances of having to look things up online and push 4 for Admissions.

At what age, I wonder, is one supposed to stop messing around with reinventing oneself according to momentary, useful but essentially limited inspiration (I want to live in Novhardok! I want to live in 1776! I want to live in 1850!) and just stick to Getting Better in a straight line?