So, in the scene after the credits, I was given the impression that the whole ME series was really an old man retelling the events of the war with the Reapers (and the events leading up to it) to a child. Then the child asks the man for just one more story (which also gives the impression that the story was told in one go), and he responds that it's late, but ultimately agrees.
Let's bounce some figures. My first playthrough of ME1: roughly 20 hours. ME2: more or less 25 hours. ME3: about the same as ME2.
The old man just told the child a 70 hour story, no **** it's late!