I have been doing a lot of reading on this lately as I am debating on the age to spay my little girl. The articles vary, but average 8-10 months. At this point, I am going to go with my own judgement for my baby. I am going to wait for her 1st or second heat cycle, depending on her age at the first one.
With my first maltese, she stopped growing between 10-12 months. Her first heat cycle came between 8-10 months.
Larger breeds can continue to grow til about age 2, but our babies are grown long before then!