I can't wait to see how big mine get!! Love them being chicks too though. Thanks for the replyWell they say full maturity is 2 years old but just like a puppy gains most of the growth in the first 6 mos and just adds a bit more size and mostly girth after that I am counting on the same thing with the rooster. So far at 4 1/2 mos old he is a full 4 inches taller than my largest hen that is a huge Buff Orpington. He only weighs as much as her though (almost 8 lbs) So I would bet now he will just start putting on weight mostly. He is already so big that getting up on on something a foot off the ground takes some effort for him. He thinks about it for a very long time.