There are cases where you need to give the same presentation or facilitate the same training multiple times. Do you need to prepare again if you already have given the presentation or facilitated the training in the past? It depends. You should always take advantage of the feedback that you got after the previous session to further improve your presentation or training.
Maybe focus a bit more on the parts that have opportunities for further improvement. It also depends on the time that past since the last presentation / training. The more time that was in between the sessions the more time you should take to prepare as you may have forgotten some parts. Do not presume that just the fact that you have done it before, you can do it again. Make sure that you properly prepare for each presentation. The time it will take to prepare may be less compared to the first time, but it will take some time to ensure you didn’t forget about some parts, practice again some parts such as the opening and closing remarks to ensure high quality.