NEVER go over your allotted time. It seems to be the one thing that will leave an audience with a negative feedback bias if you over run. Consider yourself as an audience member. You have turned up, with a view to being fully engaged with the presentation, but you have an important meeting to attend 15 minutes after the presentation ends. The closer the speaker gets to the finish line, the more anxiety builds. The threshold is when the speaker runs over time, even by a minute, as this is now having an impact on the your planned schedule. At this point, you will be more focussed on "Am I going to be late for my meeting?" than listening to the speakers final words.
It's better to finish at least a minute early, and remember, question time should be inside your presentation time, not added on.