A technical presentation is always scheduled and consequently, the speaker will, with an overrun, not only affect his or her schedule, but also the schedules of every audience member present. There are two factors in play here:

• The audience anticipates that the talk will end at a certain period of time and consequently, once five minutes remain, the audience will be waiting (and expecting) the speaker to to begin concluding, and
• The closer the speaker draws to the scheduled end-time the more the audience will be contemplating: "How will I get to my next meeting in time", and "I'm going to be late.".

The audience will have already summarized the presentation in their minds: "The topic is z, and the supporting arguments are a, b, c, and d." The addition of entirely-new points with supporting arguments will frustrate the audience.

The audience will, therefore, not be listening to anything significant said in the during the last few scheduled minutes of a presentation unless what is being said is a collection of summaries and conclusions.