You can take the quizzes and exams as many times as you like. You can set the settings to choose only questions you have not seen yet or to include questions you have seen before. The more times you take quizzes and exams, the fewer 'new' questions you'll have to draw on, but if that's OK with you, you can keep going! There's a behind the scenes video here on how to set up the quizzes etc that I found helpful:

Hi folks,

After close to a year I finally finished the precast video and ready to start the book and the practice exam. One thing I noticed and I can't seem to find the answer on the web site is how many time can I take the Premium quizzes and the mock exam in the Exam Simulator? It was probably in the product page somewhere when I first signed up, but given this long period of time I cannot seem to locate it. Much appreciated for the help in advanced!