It's all about the ergonomics
Back in 1978 or so my wife and I took a day trip from Thornton, Colorado (north side of Denver) to Pueblo, CO on my '77 RD400 Yamaha with a Vetter Windjammer fairing. It's about a 250 mile round trip. I was a lot younger then, but I don't remember being particularly tired at the end of the day. The RD had a lot less horsepower than the F800, but it handled freeway speeds just fine, even pushing that big fairing (and two up).
In 1988 I rode my Yamaha 650 Seca Turbo from San Diego, CA to Fort Collins, CO and back. On the way home I rode from Grand Junction, CO to San Diego in one day, about 840 miles. You couldn't pay me enough to make that same trip on that motorcycle today. The seat was terrible and there weren't nearly as many options for custom seats back then as are available today.
Just last year, I rode the '01 R1100RT from Albuquerque, NM to San Diego in one day, about 860 miles and I could easily done another 100 miles or more.
Like so many others have said, if you are comfortable on the motorcycle it shouldn't be a problem. Enjoy your trip!