Well I don't breed Yorkies however I did breed Goldens. We breeders never ever bred a Golden before 2 years of age. Why? Because if a good breeder is really concerned about any problems like hip dysplasia, don't remember elbows, OFA will not certify your dog until 2 years of age. Preliminary readings don't count. I had a female with a preliminary at 1 year come up OFA good. At her final reading at 2 years she came back borderline. No breeding. I don't believe in a female having 2 heats then breed. IMHO, no dog can be genetically clear until 2 years of age.
Again it is only my opinion and I speak for no one but myself
Nor am I knocking anyone who differs from my opinion. Everyone does what they feel is the best. This is just my way.