I guess that for some people, breeder female rats/mice never need a break. Case in point: I recently talked to someone who keeps their mice in pairs, all the time. So, basically, the male mates with the female before she is even done nursing her pups; let alone has had some recovery time between litters.. virtually, the female is always either pregnant or nursing, constantly.
I do not think that this is right. I give my rattie moms a respite between weaning their pups and being re-bred. I do not keep the males in with a preggo female so that he can re-breed her as soon as she has her babies. You?