Classes that are shorter and more often give the student more opportunity for periodic review. Material is not restricted to just 5 months of a semester. It can be digested and redigested at regular intervals over 10 months. This kind of review is very important to long term memory. Therefore, the student naturally remembers more.
More frequent classes increase the reminiscent effect that comes between classes.
Students increase memory when his interest is high. It is easier to hold a students interest in smaller chunks of time. Homework is part of the review process. Homework on a subject over a full year gives students the periodic review that is vital to increase long term memory. Homework in shorter doses, enables the student to have more starts, middles, and ends over the course of a year.