Before I started getting stage time giving presentations, I spent many years on the stage as a musician. In fact, you will still see me occasionally playing a few tunes in a restaurant or pub. One of the things that I learnt from playing and from listening to live music is to leave them wanting more.
I have heard great bands that just don’t know when to stop planning, or that insists of playing every song they know. What happens? Everybody gets board, and leaves before the band has finished. So when they do finish, they end to a lukewarm applause from the few people still there.
I have also heard bands finish their set with the entire audience is on the dance floor, while everybody is having a party. They end the gig with a bang, to huge applause. When this happens, everybody remembers a great party, and is back next week.
Why does this happen? Simple – the last impression is what people remember. The same applies to speaking.
If you speak for too long, people will get board and loose interest. If you finish on time, and with a strong finish, they will remember how great you were, and will want more. Next time they hear you speak, they will wait with anticipation for your presentation, and not with dread as to how long you are going to speak for.
Leave them shouting “encore”, and not “thank goodness its over”.