Many people are afraid of running out of material, so they pack too much into their time-slot. They start rushing to fit it all in, and we sense their panic.
Pack your talk as if you were packing a suitcase. Don’t you want to leave some room for some goodies you find along the way?
I had a student who planned her talks to the second. During one of her talks, she said something funny and we laughed. She waved her hands wildly to silence us.
Afterward, I asked, “Why didn’t you allow us to laugh?” She said, “I didn’t have time for you to laugh!”
If that weren’t so sad, it would be funny.
It’s better to end up with extra time than to sit on your suitcase to force it closed.