Fred Wilson got it so right in a recent blog post: postponing the preparation of your presentation slides to the very last minute and showing up exhausted to the meeting does not pay off. Books such as Brain Rules provide scientific evidence that an exhausted brain is perfectly able to survive (i.e., run away from tigers that chase you), but not really good at coming up with great ideas anymore.
Get organized, finish the work in advance.
And if you are running out of time (these things happen), make the trade-off what would contribute most to a successful meeting:
  1. Fine tuning those bullet points or re-shuffling the deck one more time
  2. Showing up well-rested, energized and able to handle the most difficult questions confidently
Your call.