Before breeding, make sure your girls is in prime condition
I understand... Before breeding, make sure your girls is in prime condition to breed (hips/elbows pre-limed or certified). Her vaccines should be up to date, dewormed and super healthy over-all. When she discharges, few days later get her to a veterinarian that is a fertility specialist. He/She will guide you from there on.
You can do BACK-TO-BACK as long as the female is healthy. We do 2-SKIP-2-SKIP-2 and retire (2-0-2-0-2). When you skip the female will need a progesterone shot (NO exception here). After each breeding she must be re-examined for optimal health - THIS IS CRUCIAL, making sure she's healthy to breed again is the main factor in breeding healthy puppies.
If you follow this method, your female will retire at 6 years old. She'll still have good 6 years left to enjoy life and be the dog she was born to be!
Breed with your heart, please... Good luck.