Until Dr. Spock came along in the late 1940s, most babies were fed on a strict schedule. The hope was that they would soon come to follow a schedule and make life easier for the parents. This schedule would also teach them that their every whim was not going to be met in this world. Some still feel this is sound advice.
Others believe in listening to the signals each infant puts out. His body sends signals of hunger when appropriate and signals of being satisfied when the right amount of milk has been taken. And almost always, this is the correct amount to promote optimal growth.
So this author counsels to feed on demand. Your baby knows best what he needs. Follow his lead with regard to feeding and you'll rarely go wrong.