Attention, Undivided and Divided

So when you watch eight hours of lecture in a row, it's not that you lose the ability to pay attention completely at some point, but that you can only pay attention for progressively shorter periods of time, with increasingly longer periods of not paying attention. Ie:
8am ~ 30 min attention time, 0.5 min not paying attention
12am ~ 10min attention time, 1 min not paying attention
5pm ~ 0.5 min attention time, 5 min not paying attention
Oh god there will be a lot of catch up.