You are at your latest around age 20.
Till Roenneberg analysed some 25,000 questionnaires from Germany and Switzerland. Chronotype grows later throughout adolescence and peaks at about 19.5 years in women and 20.9 years in men. After that the trend reverses: you shift earlier again for the rest of your life.
Useful: Roenneberg proposed this turning point as a biological marker for the end of adolescence.
Source: cet.org