Where does the 12.9% come from? Are you one of those guys that look at your usage at the end of the month and go "Damn! I only did 333GB of a potential 1.333TB"?
4/31.
And no - my heaviest usage was 55GB in a month (IIRC)
But besides that, I'm not paying for usage, I'm paying for internet access. And I'm really not concerned about not being able to download 10GB this week, I'm annoyed because I can't do anything...