Winston Churchill once said: “A good speech should be like a woman’s skirt: long enough to cover the subject and short enough to create interest.”
“Take this advice to heart. Even highly gifted speakers like Churchill would never ask an audience to listen for more than 25 minutes or so. Extending a presentation beyond half an hour will stretch any group’s attention span.” ~Richard Branson
So, exactly how long is long enough? Well…
some people will tell you to take all the time you need to get the point across. On the other hand, even with an agreeable audience, there is a time limit that you can exceed. The audience can reach a point where they are simply out of patience with any Speaker or Presenter on any topic…even their very favorite one.
Of course, frequently you are guided by the event organizer to a specific time allotment, and that of course sets the limit. Additionally, a little research will go a long way to guide you. What precedents have been set at past events?
One way good way is to set a reasonable time limit, design your part to fill that limit, video your Presentation/Speech, and finally, watch it.
Then, ask yourself this question: would I sit through this?
If not, why not? Then make the necessary adjustments to fix it.