It's becoming increasingly difficult for students to maintain a healthy work/life balance.  In practice, teachers must realize that when assignments and preparation must be done away from the classroom, there should be clear learning goals and a reasonable amount of completion time.  Otherwise, you're likely to skew your performance metrics (like grades) and increase cheating and incompletion rates.  Effective teachers know that most of the value from a class comes from time spent with a facilitating teacher and other learners.