Yorkshire terriers are considered adults at about 1 year of age. At that point their bones stop growing, although they may continue to put on weight and grow muscle.
Like other small dogs, Yorkies mature and reach their full size relatively early in life. They enter adolescence at around 5 or 6 months, when they become capable of reproduction. The adolescent period lasts approximately six months, after which adulthood begins. An adult dog has reached its maximum height.
Small dogs like Yorkies usually live longer than larger dogs. Yorkies live 12 to 15 years on average, and many live longer than that.