Here's a good indicator: If you have to use your brakes on the expressway, you're not driving well.

I'm a high speed driver. Using whatever buffer rule ( # of seconds or car lengths), and watching the car in front of the car in front of you, and checking your mirrors for the racers, you should not need to use your brakes even going 10-15-mph over the speed limit if you have to use your brakes, you're driving too fast for the situation.