Waiting with the preparation for your presentation until the last minute is not a good idea. At 3AM at night before the 9AM meeting, you are not the most creative person in the world.
The other extreme is useless as well. Preparing for a big presentation months ahead will not help you get better results. When the content is not ready, none of your colleagues are focused on it, you are simply freewheeling and wasting your time.
Sometimes I see the long lead time in big companies that prepare for a big investor day. Work starts 3 months before the deadline, but people only start to focus for real 4 weeks in advance.
And yes, the best option is somewhere in the middle: start a few weeks (up to 6) before with thinking about what you want to say. Put it aside, get back to it, maybe design one slide all the way to the end in the look and feel you want, and slowly iterate your way to presentation day.