I drive 80 between Grants Pass and northern Oregon all the time, the roads are made for those speeds.
I would never drive 55, it takes forever to get from my house to PDX at that speed.
Ed
Try the stretch between Junction and El Paso, Texas. Over 400 miles of NOTHING but a few scrub brush and tumbleweeds. That would be over eight hours of driving - taking a few breaks in the small towns out there.