Hmmm, I thought I said that I did indeed agree with the certain factors. Such as I am breeding as pet only and you are breeding for strictly feeders.
That being said, most of my rats throw more than 15 young (more like 22 is an average) and all (with limited exception) reach weaned and past.
As far as giving them breaks, it depends on the break you give them. I'm sorry, but I don't agree with letting a male breed a female right after giving birth to a litter. I've seen breeders that give them 2 weeks and then breed them again.
And I said feeder breeder produce 12-15 months. With the breeders I know that give females breaks, I've seen these females produce large litters at 18 months and over.
But again, whatever works for you.
wow 22 is an average....you should write a book
That is a sincere statement especially since you are claiming that all survive.
I have been doing this for a very long time and never ever seen a litter of 22.