There are two major problems created as you keep increasing the dose of Adderall. First, the risk of significant cardiovascular consequences increases. Second, the more Adderall you take during the day, the lower you sink at night when the Adderall wears off and your body actually starts the beginning of withdrawal. At night you sink below what would be your normal mental levels. Therefore, in the morning, it will take longer for the Adderall to bring you to a satisfactory performance level because it has to take you from the valley it brought you into at night, to your normal performance level, and than to a satisfactory performance level. In short, the higher the dose, the deeper is the valley at night; the deeper the valley, the longer it will take in the morning it will take before a satisfactory performance level is reached.