I voted 3.5 also. 3.5 here is an ancient deer, but in general that is when their growth matures (note that is not their peak, but maturity). There is a very big jump in antler development from 2.5 to 3.5. 4.5 year olds are most certainly bigger than 3.5 year olds, but the jump is not as significant in most cases. I believe that deer peak around 5.5, but finding one of those in PA that is actually visible is very difficult.