every one of my snakes i get, i will offer food the first day. Its just something i do to see if they will be a strong feeder and it makes me not disturb them to much as they are getting acclimated into their new home. only my black pastel did not get fed because he got fed 2 days before he arrived, but waited 3 more days to feed him and he has not turned down a meal since even while in shed. i personally don't feel you need to wait for a snake that has been a constant feeder up until you acquired him/her because some breeders feed every 5 days compared to some who feed only every 7 days. but every snake is different and some may need some more time to settle down until they will feed, but if they have been a strong feeder before that there is really nothing to worry about long as they don't lose to much weight. I personally like the 7 day feeding cycle because it works out for me with work(only off sundays and mondays).
Tom