I am a national trainer for a major medical facility, and I facilitate 4 hour PowerPoint presentations 3x per week every other week. Plus, I travel to other hospitals across the country to train their hospital staff with the same 4 hour PowerPoint presentations. I practice, practice, practice, practice, and practiced my presentation to the point of memorization. I still stutter, but now I really enjoy training 10 to 100 people every session. You do what is right for you. Good luck