Think with the Kingsnakes it depends on size rather than age, as some Kingsnakes can be "Pushed" with frequent feedings to get it up to breeding size within a year!!...This is in my opinion is not a good idea!
With usual feedings of once a week your Kings should be breeding size in about three years time. In general females can be bred at about 300grams and males at 200grams.
Your breeders should be fit and healthy with good body weight, but not obese as reproducing puts an unfair stress on snakes that are not in the best of health. You will also need to brumate your breeders for about four months to get them ready for the breeding season in the spring.
Triangulum will maybee post, and help out as he is the resident expert!
