the length and weight of corn snakes will depend on Genetics. I have a male snow that is 3.5 years old, and is a little over 5 foot, weighing in around 300 grams or so. my Female snow, is older about 4.5 years, only about 3.5 foot long, and weighing in right around 200. I bought the Female from CAV, and he had her from a pretty young age. He told me that she hasn't gotten any bigger, and neither did her clutch mate.
I believe that Cathy Love states in her book somewhere about the size difference between male and female. you might want to look there.