I feed my hatchling ball pythons adult mice twice a week. As they grow I'll feed multiple mice in about an hour, or switch up to a small rat. I usually keep feeding twice a week until they start looking a bit fat, like a sausage LOL. Then I'll cut back. I usually base my feeding on the appearance of the snake, and even adult mice can have a huge difference in size. My fancy mice mature much smaller than just a regular white feeder mouse. I'm actually in the process of changing all my mice and rats over to just pure white rodents, the white mice mature faster and get bigger and I don't have to choose among my various color patterns to feed them off, I've actually gotten attached to some of my fancier mice and they are nearing the end of their life (about one year), so they need to be replaced anyway.
Here's a photo I found on the web, I'd say if your ball python is this fat it's time to slow down on the food. I like to keep my snakes plump, close to this but not quite this fat, I try to never get my snakes this fat, this looks very unhealthy.
http://i180.photobucket.com/albums/x...3/DSCF0302.jpg
Now if your snake looks like this I'd say he's a bit thin and needs to eat some more:
http://i62.tinypic.com/mvkot3.jpg