If I talk about studying the opening, what I mean is studying both the opening AND the ensuing middlegame. You have to think of both as an inseperable unit. Imagine you would only learn the first 12 moves by heart without understanding the logic of the position and completely disregarding what comes next. In your games you would find yourself in a very specific situation, with very specific underlying principles. Facing an informed opponent, while being ignorant yourself would put you in a highly unfavorable situation. You would be playing with a handicap. Only if you study the most important pawn structures within the framework of your opening, the strategic goals and typical maneuvers, as well as the recurring tactical motifs, you can call yourself to be really prepared for the battle.
My analyses take this structural connection between opening and middlegame into account. In some occasions, the material stretches out far beyond move 30. In every instance, there is a verbal explanation of the underlying strategic goals and principles. This will mitigate the consequences of forgetting concrete lines, as you will be able to use the presented opening logic as a compass.