You are given an UNLIMITED number of times you may start and stop taking the course. Take it every five minutes if that works for you. We don't care. UNTIL you get to the final exam. You are allowed two attempts to pass the exam, with a score of 80. If you fail the exam twice, you may retake the course free. Send a ticket to request the additional time needed. 

BUT let's be practical. The best practice is to take the exam as soon as possible after completing the course to give yourself a better chance of passing the exam.