I thought I recalled hearing it was originally 5 hours. According to the ABC website's schedule right now, it's going to air from 8:00 - 10:30 pm tonight, and from 8:00 -10:00 pm, with a cut for the President's speech inbetween.
So, that means we get 2 hours 30 minutes tonight, and (assuming the President's speech is about 20 minutes) 1 hour 40 minutes tomorrow, for a total of 4 hours 10 minutes. In reality, they will have cut 50 minutes, the cowards....
Sorry I should have been more specific. They did not have time to show all hours to the people at the first screening. That is why they gave them the second tape to take home and watch.