Fit your talk to the allotted time
Many consider it almost a capital crime for a speaker to exceed her
allotted time. It is not unusual for a session chairperson at a conference to be quite abrupt with a speaker who rambles on
after the timer has sounded. Even in less formal settings, a
speaker who ignores the prescribed time limit will quickly
alienate nearly every one in the audience. Never, ever, speak
past your allotted time. To do so is extremely egotistical, and
even if your audience is courteous enough to let you continue,
they will not forgive your rudeness