Preparing for 100s of topics is a colossal waste of time. Essay tests your analytical and critical writing skills, not your cramming capability. By preparing more than 10 essays you guys will not only waste your time but also become a victim of 'information overload' and when the paper is in front of you, either everything would vanish from your mind or you would waste 3 hours on deciding what to write or not.

My suggestion would be to stick to 'originality' and have faith in your own skills rather than cramming essays.