I tend to work on presentation design projects in bursts: dive in, get stuck, put it away, work on another project, get back to it, put it away again.
Even when you stop working on something consciously, your subconscious mind continues to chew on things. This article discusses recent research that proves that the subconscious brain can solve real problems.
There is another benefit of this delayed approach. When you get back into things some details of the story have faded to the background a bit. It is this "numb" state of mind that is useful to piece together the story that really matters, you have to explain it to yourself again and it might come out clearer without the distraction of these details. In addition, other details might come to the forefront which you thoughts were not important.
All of this explains why presentations that are created at 3AM at night before the 9AM meeting are not very creative (most management consulting projects). It also explains why an outsider or senior executive/partner can walk into a room and articulate a story much better in 3 minutes than an entire team who has been working on it 24/7 for the past 3 months. It not all experience, it is also being able to take some distance from the subject.
What to do? Start thinking early about the presentation of your results. The problem of how to communicate your project, is a different one from the problem that your project solved (read that sentence again). While you still might end up finishing your presentation at 3AM, if you started early enough to think about it, your presentation will be much more effective.