Took the 6:20 United flight to JFK 3 weeks ago. I got out of the taxi at 5:00. In the next 11 minutes, I:
-checked in for Intl Flight connection to LHR at Premier check-in
-cleared security (it was a joke)
-took people mover to sketchy commuter terminal
For those not familiar with IAD, this is a land speed record. My travelling companion arrived at 4:30 (and yes, the United counters were open), and he had a longer wait than I did.
For what it's worth, though, the flight loads for the entire airport then were a lot lighter than now...