Why is it common for people to go over time when presenting?
1) Getting THROUGH THEIR CONTENT is a top motivation.
2) They plan as if for a recital but find their instinct, in the moment, is to be spontaneous.
3) Their ego takes over and, out of anxiety or enjoyment, they lose sight of others.
4) They do not anticipate the audience's need for a conversational exchange.
All these problems are built into the mainstream, one-way, linear, slide-heavy presentation paradigm. Our brains have a conversational design. Embrace that and managing time becomes the easy part.