The primary reason for aging deer is to manage for mature trophy bucks. In order to produce trophy deer, three (3) things are needed: Age, Nutrition and Genetics. It is impossible to manage a deer herd without knowing the age structure of the herd! Whitetail bucks reach maximum antler size at 6½ to 7½ years of age. Bucks will not reach their full genetic potential if they are harvested before reaching maturity.