Mine is 20 months and she has stayed at 68 pounds since she was a year. She is 28 inches tall, so she looks very lean, but she is healthy and that is all that counts. Mine is like a bullet, she is super fast and even though she is tall, her body does well for things like agility, which she loves. The vet says she is ideal and wouldn't push her putting to much more weight on, so 70-72 pounds is where she can be, but anything over that she would be considered over weight. So I'm thinking that since mine is super tall and the norm would be about 24-25 inch for a female, then 70 pounds would be a good weight.