A friend was looking for a topic for a freshman term paper. He found a theory that sounded interesting and researched and wrote a successful paper. Next semester, in a different course he was able to use the same theory from a different angle and wrote another successful paper. The pattern continued the next year and the next and on until graduation. In graduate school the theory worked again all the way to doctoral studies. Now this was not the same paper mind you, and the sophistication and research increased dramatically at each level. But the confidence in the theory and the base of work behind it made for good papers in the future.
My friend had found a concept that in the sports world is known as the sweet spot. In most sports that require contact with a ball the instrument used has an area where the ball is propelled in maximum velocity off of the surface. It seems as if the effort expended is not as great as when the sweet spot is missed. This concept is talked about in baseball, tennis and golf and in many other sports. In golf, hitting a ball in the correct place on the clubface or the sweet spot will result in a straight shot with power and distance. Ben Hogan, one of history’s greatest golfers was said to have a worn spot on the face of his clubs the size of a dime, exactly where the sweet spot of the club was. This dime-sized spot was made there by repeated hits on the golf ball in the same space.
In public speaking, you have and can develop a sweet spot too. This could be a topic that you know a great deal about or one that inspires great passion about. In many ways you can explore various themes of this with the same audience and have a successful speaking career. Just like my friend above you can layer on sophistication and new light on your topic to the delight of yourself and your audience.
Or, you can present the same speech to different groups, polishing as you go along until you have reached a gem of speech that can be in your tool box forever. An example of this could be an evangelist that explores the themes of grace and forgiveness for different audiences all over the country and the world.
The key here is your passion. If you approach even the same topic with fresh eyes and enthusiasm, you will be energized and so will your audience.