Gone in 45 mins

I have an Algorithms class from 3.30 to 4.45 PM on Tuesdays and Thursdays. To be frank, I rarely ever focus fully in this class. I am always in a half-dazed state. Not that I feel sleepy in class or anything. It is just that I cannot bring myself to listen to the lecture. The rambling style of the prof doesn't help matters much. But anyways, the one thing I learnt from this course: I know my attention span precisely to a minute. And it is exactly 45 minutes. Yup, everyday as I sit through this class, I will glance at my watch exactly at 4.15 PM for the first time. After that, it is 10 minute increments of glancing. The initial 45 minutes, I at least try to listen with half an ear. After that, it is all downhill.
Anyways, I just wonder how it is that people sit for hours together listening to lectures or even watch movies. The other day, my friend told me he watched 4 movies back to back. These days, I can't sit through a single tamil movie in one sitting. I start fidgeting after an hour or so. Maybe this is just a reflection on the sad state of movies or MAYBE I am getting old!!