All dogs are physically mature at one year of age. So for breeding or changing to adult dog food, one year is a good age. It is good to have dogs spayed or neutered at six months. Some larger breeds of dogs take longer to become emotionally mature and to calm down and stop exhibiting puppyish behaviors.
Well, from my experience, they vary, can be from 1 year to 3 years, but either way they always grow so your puppy shal be bigger each week, even if you don't notice it until a month has gone by. :)