I remember how skeptical I was looking at some presenters traveling around to multiple conferences with "the same" presentation a decade or so ago. Having been a course instructor for years and being a presenter for even longer, it looks completely different now. It's not that the topics you cover under the same looking umbrella can be quite different, you also find much better ways to express whatever you want to tell your audience as you experience feedback.
Of course the best would be to present your story crystal clear from the start, but despite being an enthusiastic follower of Garr Reynolds and Nancy Duarte, you'll undoubtedly need lots of time anyway to take a relaxed look on your story and distill to the level needed to form a great presentation. I've actually found it quite hard to refine my slides without actually showing/presenting them to an audience. The faces, questions, smiles and sometimes plain staring expressions you get tell you how you'd done and you can derive ways of how can you improve.
Two interesting examples are my slides on Drupal 7 and localize.drupal.org.
"What's up with Drupal 7?" slides
I did multiple introductions to Drupal 7 at the local drupal meetups, the local Drupal conference and two Drupalcamps around the region. While I based my initial slides on Angie Byron's deck from Drupalcon Paris 2009, it eventually proved to be inefficient to wrap my mind around her thinking, so I did substantial reorganization for the Drupalcamp Prague session. Eventually I found the usual slide structure limiting enough I decided to redo the presentation in Prezi, and that (despite myself still being a Prezi newbie) worked out well. You can compare the two versions from Drupalcamp Prague and Drupalcamp Vienna respectively:
Prezi proved to be a very good tool for deep-diving into various topics, especially when new Drupal admin tools were presented on screenshots. Showing a screenshot and then moving in/out of the newly added Drupal 7 elements was nicely supported by the zooming nature of this presentation environment.
Translate Drupal! slides
My slides on localize.drupal.org evolved with the understanding of where that service leads and how can we make progress in integrating several language teams there. I've kept using the same presentation shell in this case, reusing the same images and basically the same overarching structure. The content and visualizations changed a lot though.
Amazingly, my first take on it concentrated more on the history in a fancy metro-map way, but when you are about to talk about crazy cool new technology, you should not take much time for the history as I eventually came to conclude. The "second pass" I presented in Prague had more time for demo, which was useful given that we had more fun stuff to show by that time. I was still getting "strange" questions, and it became evident to me that I'm not good at explaining how localize.drupal.org is replacing and enhancing certain parts of the workflow. Where does it still lack tools and where is it not planned to have more anyway. So for Drupalcamp Vienna, I decided to take the sharing workflow figure and present the localize.drupal.org flow on top of that. I think this explained how localize.drupal.org helps and what are the directions much more clearly, then the one sentence per-slide "schoolbook" points I had previously.
Your iterations
While before/after slide examples are common in presentation literature, the evolution of presentations around a topic are harder to find. I'm sharing these slides in part due to my interest is growing this pool. Do you have similar presentation evolutions to share? I'd love to see them.