If you do it that way you need even more rats because each female will be on a 3 month cycle. 1 month gestation one month nurseing until weaned then 1 month gestation again. I do plan to do exactly this because I think you will get a better yield and your females will live longer and have bigger litters I believe. But the earlier mentioned 1 female per snake will not work with this method for sure. I would probably go with at least 2 females per snake or maybe 5 females per 2 snakes.