A couple of people here have done the Iron Butt thing on their America. 1,000 miles within 24 hours. My max is about 573 miles in one day and I was ready to get off.
If you put the 19 tooth sprocket on your bike, cruising 75-80 is a breeze. You're not searching for another gear.

"Catching a yellow jacket in your shirt at seventy miles per hour can double your vocabulary" Author unknown