You can feed babies every four days but they do fine at once a week also.
This is setting pretty high expectations for a ball eating wise. Very, very few of them will eat anytime something is offered even when they are on a regular schedule. If a ball is constantly moving around something is usually up. Hungry, environment off, looking for love... Sometimes they will move around a bit but it doesn't last. A ball that does nothing is usually a "happy" guy.