I'd like to say that when I become a professor I will never become a grumpy *Ignore me, I am a weenie*. Who knows though, maybe dealing with large amounts of people who DON"T care about your class and don't want to do work will become annoying after a while.
A grumpy person is a grumpy person though...and the professors who have been at my school for 30-40 years don't take s#*$, and they do things their way or the highway