Younger snakes grow at a faster pace and change prey sizes more frequently than older snakes. I usually don’t buy more than 25 of one prey size for young snakes. I know the snake will finish them off even if I have to feed doubles before moving up to the next size. I feed a varied diet to my snakes so I try to keep at least 2 prey sizes/types on hand. If my snake is eating small rats, I’ll also keep and feed them medium rats, chicks, and jumbo mice.