No. You need not add course each time. Once you add a course, you have to add batches inside it as and when needed. Students will be admitted to that batch in that course.
Suppose if the course is BSc Physics.
Course: BSc Physics
Section: Sem 1
Batch : Jan 2013
Now the next batch of students in Sem 1 BSc Physics may be in June or Dec.
So you can create a batch under the course BSc Physics
Course: BSc Physics
Section: Sem 1
Batch: June 2013, Dec 2013.
So you can go on creating the batches inside the Course.