Most experts say to breed your female After 2 years old (or the 3rd heat) and Before 10 years old. They also suggest every OTHER heat (about once a year). The main factor is how your female is doing. If the breeding is hard on her then go lightly and if she is one of those that just bounce right back then once a year is good too. It really depends on her health as to when to stop breeding (as far as the female goes). Also, if there is not a big demand for puppies in your area, then you might want to re-adjust your schedule.