you can call it a newbie question if you want, but as far as why I asked it, if you had read the post that you replied to, it said
"I have been keeping reptiles for 30 years, I just never bought food that far in advance before. I can't remember what ages different snakes were when I bumped them up to their next size prey, I always judged by their current size, appetite, how long before defecating after eating, etc etc. "