When the introduction of the JAR exams was being planned the intention was that students would be required to take all 14 exams in a single sitting. After much debate this was amended to allow two blocks of exams.
The approval for each course includes a specified teaching structure, which must be followed. Most of the schools went for two blocks, but some have now moved to three blocks to make life a little easier for the students.
Students are not obliged to take the exams immediately after completing a block of study. But before you can take an exam you must have completed the specified training for that subject. You can then take the exams in whatever size blocks you like, provided you complete all 14 within:
a. 18 months from taking the first exam.
b. 4 attempts at each exam.
c. 6 visits to the exam centre.