I feed rabbits to my two biggest snakes, an 8 foot female BCI and a 9 and a half foot female BCI, and we get them from a local supplier so we don't even have to pay shipping! They get an appropriately sized rabbit every two or three weeks, depending on their behavior, time of the year, and their bathroom habits. We order about 4 medium rabbits per month.

My 8 foot female (Our first snake) was absolutely OBESE at 6 and a half feet, and our vet actually suggested switching her to rabbits, which I hadn't ever even considered up until that point, and with appropriately sized (barely left a bulge) bunnies, she managed to grow out of her chubby stage and slim down to a more respectable and healthy weight.

Of course, I do have an 8 foot Guyana BCC female that just plain does better on rats. It really depends on the snake.