Saw something that said the average NFL game length is 3 hours 11 minutes for 2013. So a game that starts around 8:30 PM should end around 11:40 PM. I didn't see a breakdown, but I would bet those night games last longer, it seems those games regularly last past midnight.
As a person that has lived on both the East and West coasts, the West is far and away better for sports viewing.