I know a few people who breed the same girls every year. I personally, prefer to breed them every other year. Thus I have group A and group B. I still breed every year, just with different girls. It makes me feel better about their overall health. Occasionally if a female gains all her weight back and then some, and also starts exhibiting signs of being ready to go again, I'll trust her judgment and let her go two years in a row. But then she definitely gets a year off. Just my .02

Cheers,
Kat