Rats dont take that long to defrost. looking at how many snakes you got then I would agree with the 30 min marker. But if you throw them in the fridge the night before then all you would have to do is warm them up in water and be done. Say 10 min to warm them up but I wouldnt do them all in one sitting because by the time you get the first 3 to feed then the ohter ones would be cold. So I would only warm up 2 or 3 at a time uless your snakes just eat really fast. But it only takes 1 snake not eating to cool your rats. But that just depends on how your babies eat.