I completed the MQ several times in Oblivion with multiple characters.
QUOTE(Grits @ Oct 8 2013, 10:42 AM)

Despite precautions I’m concerned that there will be a feeling of the game being over once that part is complete.
That is the problem I encountered every time one of my characters finished the MQ. The game felt over. Everything else that I could do felt pointless. I could play forever as long as I don't finish the MQ. Like someone else said, it's hard to go back to killing rats after foiling Dagon.