Most call schedules for intern years run either every third or every fourth night on call. There are a few states that limit the number of hours that a resident can work. Perhaps the most prominent state with a such a law is New York. New York's law, limiting residents to 80 hours per week, came about largely due to the Libby Zion case. Libby Zion was a young woman whose death in a NYC teaching hospital sparked an investigation into the large amount of hours that residents work.
Many boards require recertification at regular intervals.
Before discussing this, it may be useful to delineate the differences between organizations that physicians may be associated with. College - Similar to an association, but membership is often tied to board certification and experience. As of yet, this has not been implemented. Applicants face 10 simulated patients and be evaluated on their ability to take a history, perform a physical exam and record a written note. A physician's education does not end with medical school and residency.