I have 2 chicks they are about 5weeks old. I also have 3 chicken that are 1 year old when is the best time or how old do the chick have be put in the coop and run with the older chickens.
There is a nice article on this in the learning center here called "Adding New chickens to your flock"
It may help answer your question.
We are what we repeatedly do. Excellence then, is not an act, but a habit.