It all depends on the bloodline. Hatchery large breed Cochins will fully mature in around 8-10 months and will lay fairly well year round as long as you don't let them go broody. On the other hand my show quality large breed Black Cochins aren't fully mature until they are a little over 2 years old. And will be nearly twice as large as the hatcheries. And they lay fairly well in the spring and early summer, but totally stop through late summer- early winter.