I will be buying 2 buff orpington chicks soon. I helped to raise lots of chickens as a kid, but I have no idea how much bedding material to purchase. I have seen 60L bags, 1000-cubic inch bags, etc. I am so lost. Since I will only have 2 chickens total the coop I am building will not be very big. Will a 60L bag be ok? How long would that last if I put a thin layer only?