Feedback should be neither the main focus of study nor something that is left to the last couple of weeks. It should be used throughout the course to back up your main study material.
This is why most schools continuously update their progress tests to include feedback questions. If you get to the end of part of the study material but cannot answer feedback questions on it then your studies of that area are incomplete.
To develop a thorough knowledge and understanding of a subject and to keep the relevant information in your working memory, you must use that knowledge, understanding and memory as frequently as possible. After studying each section of material you should conduct question and answer sessions using feedback material. Most people gain far more from trying to answer questions than from simply reading their notes.
There is no point in developing what you think is a thorough knowledge of a subject only to find that you cannot answer any of the exam questions. This is what people mean when they say " I know all about the subject but failed the exams....those exams are all a load of ......." The real problem here is usually that they have developed the ability to regurgitate data from text books but cannot apply that knowledge to solving problems.
By using feedback on a regular basis you will be able to fine tune your study efforts in the correct manner to store knowledge and be able to use it in the exams.
The vast majority of students find that they learn more during the last two weeks of their course than at any other time. It is no conincidence that this last two weeks is usually devoted almost exclusively to practicing answerring feedback questions.
Make sure you get the balance right.....study the notes AND practice with feedback questions. If you limit your efforts to either one of these activities you will probably fail. But don't just learn the ANSWERS to those questions, learn WHY THEY ARE THE CORRECT ANSWERS and how to answer DIFFERENT QUESTIONS on the same subjects.