I strongly believe, if students not understand up to that point why they need to complete all previous courses, they will face with the pure true; without having the basic understandings it is very hard to follow - even the easiest - demonstration, not talking about to  understand them. Also, if students spend time to practice on their own and/or read/watch all related comments or TechHelp videos, that course can be easily more than 4hours length. It is a carefully and greatly balanced course for all levels.