As for long-term memory, most of what we learn is forgotten rapidly unless special care is taken to help retention. As students take notes, very little is actually retained without some helps to crystallize particular points. The use of the chalkboard, visual aids, handouts, buzz groups, and questioning are often effective helps. Rehearsal and imaging can improve learning. Often students do not remember points from a lecture or a discussion because they gave no real thought to the issues at the specific time.
Repetition can be valuable.
Also, repeating focuses on those issues selected as important. Periodic summaries help to fill gaps for students as well as help them to understand relationships. If done effectively, it encourages student rehearsal and imaging. We learn differently when we use our various senses. In most cases, using more than just one sense is more effective.