My average speed is usually fairly ideal. The majority of my drive to work is 45 mph with a little bit of 35 mph on each end (14 miles daily). The rest of my commuting is around town, so speed limits of 35 mph. Its easy not incredibly hard to knock out 60+ mpg trips, and 70+ if there isn't traffic. Once a week I take a 26 miles trip to pickup and drop off a friend for church. This is on the interstate with a speed limit of 65 and I usually do 60-65 mph. The Metro does not like these speeds.
The down side of all of my trips is they're almost all very short. My daily commute is 7 miles. My trips around town are 5 miles or less. Overcoming cold start is a big thing for me.