As I understand Hughes policy once you cross the threshold it takes time to get back to normal access.  Movies, youtube, itunes, auto updates all could be using up your allotment.  Plus the varmits that might be accessing your system like Trojans and viruses.

Local fertilizer company got Huges to connect remote stores with the home office computer because no other high speed internet available.  Removed DTN and put a computer on the counter so farmers could watch markets and weather.  First week they had it people got to watching Youtube vides ("Have you seen... ?") and wento over the Fair Access limit.  Took them a week to get back to normal.