Join Date: Nov 2003
Location: N. Central Arkansas
height continues slowly increasing until the growth plates close. That's a ballpark of 18 months. Then they fill out until between 3 & 4 years old.
Whether they are intact or altered also plays a huge factor in growth patterns.
Your breeder should be able to give you a more accurate ballpark of when you can expect the last big growth spurt. Some lines will do most of their growing early and only add 1" or less after 7 months. Others might have several big growth spurts over the first 1 1/2 years with little discernible change in between. Others simply grow at a slow and steady pace for most of that time.