During the first few months of life, budgies grow rapidly and gain most of their weight. Their feathers also grow quickly, and they will gradually develop their adult coloration. Budgies molt (shed their feathers) once or twice a year, usually in the spring and fall.
Once they reach their full size, budgies will typically maintain their weight and appearance for several years. They can live for up to 15 years or longer with proper care.