At keynote level, if I run a minute over, I am in genuine trouble. A lot of people depend on that schedule, and going over time is about the worst thing you can do on a stage. It is the thing most likely to stop you being asked back.

It matters in smaller rooms, too. There is nothing worse than wasting people’s time. If you tell them it is going to be thirty minutes, it had better be thirty minutes.

I say this as someone who once ran to nine minutes in a five-minute slot, in rehearsal for a keynote demo. I was lucky: the keynote made room for it. Most of the time, it won’t.

So know your timing before you walk on. Count the words in your script, divide by your speaking pace, and then rehearse the whole thing end to end, without stopping.