My commute is totally flat and I ride a steady hard pace from begining to end that is fairly consisent day to day (+/-0.5mph average). There is no pushing it harder or letting up. I ride hard the whole way and end up cruising at the same speed within +/-1mph (except of course for slow/down accelerate for stops) for pretty much the whole 8.5mi commute. I actually don't like to go slower as it messes up this consistency which is why I always pass slower riders and ride the same speed after the pass.

Al