Traditionally, colleges are divided into the two year schools (which grant associate degrees) and four year schools (which grant bachelor degrees). However, Newsweek recently published an article about why college should not take four years. The gist of the article is that a three year college education can be a good idea. Being a professor and an adviser, I have some opinions on this matter.
The main reason for the three year degree is economic. From the standpoint of the student, completing a degree in three years rather than four (or more-many students take 5-7 years) can result in considerable savings.
From the standpoint of a college, getting students through in three years can also be more economically efficient, provided that the school is set up to move students efficiently and take advantage of this. Obviously, simply having a student graduate in three years means that the school might well be losing out on money it would have received from that fourth year.
A school can, however, benefit considerably from a three year approach. Under the traditional system (which dates back to the pre-industrial agricultural calender) schools close for long winter and very long summer breaks. This means that the facilities are idle for considerable periods of time, though they still must be maintained. Also, while faculty might be off (and unpaid) for the summer, the year round staff and administrators are still there, drawing pay and using resources.
Many schools, such as Florida A&M University (where I teach) , do have summer classes. However, the summer semester(s) tends to be quite limited compared to a normal semester. For example, I teach four classes in a normal semester and only one in the summer. While having a full summer semester would involve paying out more to faculty, this would also mean that there would be greater income and that the buildings would be fully used (as opposed to cooling and lighting many empty classrooms and offices). Of course, I rather like having a summer break, even if it is unpaid. But, getting a 33% increase in my salary would be rather tempting.
Of course, to make the three year degree a reality would require more than converting the summer to a third full semester (or full quarter). Most students take longer than four years to graduate not because of the lack of summer classes, but for other reasons. One reason is that some students need or chose to work and this cuts into their available hours (and often their GPA). Another reason is that students often change their majors, are advised poorly or make poor schedule choices that slow down their graduation progress. A third reason is that some students simply fail classes and hence have to repeat them. Countering these problems would involve making education less expensive (or providing more support), having better advising for students, and for students to do what it takes to pass.
Of course, there are downsides to the three year degree. First, a student will miss out on a year of activities such as sports, social activities, clubs and so on. Much of the college experience is what happens outside of the classroom and missing out on 25% of this can rob a student of a very valuable part of their education and experience. Second, while a student can pack a four year degree into three years, there is the question of whether or not this rush results in a loss of educational value. After all, learning is not a race but rather a process and this process might not just be a matter of grinding hours but also having the time to go through a process of maturing and learning. Third, to graduate in three years a student must know what she wants to do, be properly advised and stick to the plan. While this can be done (I graduated in three years and one semester, even without taking a summer class), it would be a challenge for most people.
I do think that the three year option is a good idea and I do think that letting a campus sit idle (or mostly idle) over the summer does waste resources. However, there does seem to still be value in the four year degree approach.
I think the professors would burn out.
It would seem that none of the student-related problems you mention in your penultimate paragraph are a problem, if students have the option to complete their degrees in four or more years.