I have had this discussion with a awesome vet in Michigan when I lived there and breed Mini Pins, and with my awesome vet here in Alabama with the Yorkies. Since most females are almost a year and half for their second heat cycle I was told by BOTH vets to breed back to back, then rest my females, then go to every other heat cycle. It is easier on them when they are younger, so it is in their best interest to breed accordingly. NOT a money issue for me.... Now, this is providing there are no complications with the whole process. I don't know about anyone else here but once my females go into heat they are vet checked before they are presented to their stud, this is my practice. As well they are seen by the vet at least twice before they whelp. Their safety and well being is very important to me. I think I have only read of one breeding member respond to when they retire their females from breeding. So, I will jump out there and ask this question
When do you retire your females???? My answer is depending on the females, some are retired sooner than others. But no longer than 5 years of age. This is approximately 3 to 4 litters. I am sure that the rest of the breeders here on YT can tell you as a whole yorkies love to be mommies and are very devoted to their litters...
So this is my 2 cents worth....