Forgetting is most rapid right after learning. Relearning is easier if it is done quickly. Don't wait until it's all gone. Space initial early reviews to support original learning. Several brief periods spread over 5 or 10 days is usually enough to ensure good recall for intermediate review.
Intermediate review is important when work is spread out over several weeks or longer.
No new learning takes place, except to draw together the final main currents of thought. Review entire semester's work in 2-4 hours. Outline and organize from memory. Don't bother copying. 60 minutes used in 3 groups of 20 minutes each is more effective than 60 minutes used all at the same time.