Everybody has their own unique level of confidence in their ability to learn and apply new concepts. Some of us are very detailed and conservative and will turn a concept over many times before we feel confident that we will be able to interpret and apply the concept in real-world exam questions. However, some of us only need to consider a concept once to feel confident that we know enough to apply that concept to an exam scenario. So, depending on your personal style of learning, you will need more or less time to prepare.