[Chris]

I'm a big older guy in Georgia and I travel on the interstates very often on my GZ250. This does not hurt the bike in the least, in fact it is probably good for it.
I am riding in the far right lane and even the trucks don't bother me a bit. I think five hours on the interstate would be safer than seven hours on the country highways. Interstates are always safer than other roads. I take a lot of breaks. Also I stop and even on the interstate I take walks in the woods to water a tree.
I wear a full face helmet, sunglasses, and ear plugs. And, when traveling, I velcro my leather jacket sleeves closed tightly so no wind gets in. I wear four or five layers on top and at least two on the bottom. When cool I wear two sets of long underwear under my jeans. Then I use the laces in my boots to tie around the bottom of my jeans. Any incoming wind at all will hurt you on a day less than 60 degrees. Warmer is better.
I usually ride about 70mph, sometimes faster if the road is smooth, but I am not really in a hurry. To me being in a hurry is not what my motorcycling is all about. Yesterday I rode 120 miles on country roads. No interstates were available for that trip. It was 55 degrees, too cool to really enjoy the ride. On a long trip the coolness really cuts into you.
You've had some good advice here. Perhaps the best is to try a shorter trip somewhere. Ride 50 miles on any interstate, have lunch, ride back. That will tell you a lot.

Chris, retired near Atlanta