appropriate expressway speed?

Back in the 80's I was Wagon Master on a tour with about 25 Airstreams with the WBCCI. Each day we knew were we would finish the day. So every one could get up and haul or run with the group at 55-60ish mph. As the leader I started with about half the group behind me, rest did not want to go slower and just took off at faster speeds. To make a long story short. Each day the group behind me got longer and fewer did the jackrabbit runs. It cost them far more fuel, They made an extra fuel stop, often beating the group by only min or behind the group at the end of the day. The cost per min in dollars and stress for them soon was not worth it to them and they just fell in the group. At the end of our 7,000 mile trip we all ran together. We figured a days travel at over all, 50 mph. Always gave us time to fuel, eat ect and still end up where we were going on time.

A few years back I told that to a friend. We traveled to the same places but he liked to go faster so we just would meet up at the end of the day. Long story short. Long trip. Wifes on cell phones both keeping time and records of fuel ect. Him, traveling 75-85 in his rig when he could. I stuck to my 60ish. His extra fuel stop each day cost him time and we ended up getting to our stopping point with in min of each other. He still likes his high speed runs as he loves to go fast, be in the left lane and pass other RV's no matter what it cost. Does complain about the road rage he keeps getting.