I took all the posted speeds at the higher end when specified. The average speed came to 63.43 mph. It is probably a little slower. I omitted the 105 mph as that's just not normal and not their usual speed.
Of 61 noted speeds - 5 were 70 mph or over. Certainly not the majority. And by the results it seems I'm pushing it a little at 68. I plan to change this up on my next trip and really watch the fuel consumption to see if there is a noticeable change. I get 10 -11.5 now.
The consensus seems to be safety first. It's comforting to know most people have their fellow travelers and their families in mind when traveling down the road. :)