This blog post on Physics Central reports on a survey of students of various majors. One of the survey question is on how much time the students spent per week studying the subject. Physics majors came in 2nd, just behind engineering, in the number of hours per week studying the material.
According to a survey of hundreds of thousands of college students in the U.S. and Canada, 36 percent of physics seniors spend 21+ hours preparing for class every week. Only one other group out-studied the physics majors: engineering students. 42 percent of engineering seniors devoted 21 or more hours to studying every week.There are more to the survey than just this, so you can read the rest either in that blog, or from the actual survey itself. And you can draw your own conclusions from them.