It is going to depend on how tall your passenger is. Gail is just 5ft 1in, sitting behind my 6ft, her nose was about level with the top of my helmet. With the stock screen, she had a tremendous amount of buffeting from the front, that really kicked in above 50mph.
We replaced the screen with an xxl clearview, and now cruise in the top 70's, with no problems. The screen has been tested to 93mph and should be good for higher than that, but we don't have a need for that kind of speed. WE not I.
For the rest of it, Gail has just the right leg length to have her feet flat on the foot rests. Our trips involve a stop after about every hour in the seat, 10 minutes off the bike if just for fuel, 20 to 30 if it is coffee or a meal.
The most we have done in a day is 370 miles, over 10 hours, but we never go from A to B, we take in all the other 24 letters. In Wales we saw a sign for "Water breaks it neck". Turned out to be a waterfall, but nothing really great the day we went 40 miles off course to have a look, as we were in the middle of a drought (Meaning it has not rained here in England for 4 days). On the motorway, keep up with the traffic, on the by roads, just tootle along.
We have done a trip to Rheims, 7 days in Devon/Cornwall and 5 days in Wales on the bike, and have 7 days planned in our Lake District starting April 2nd.
Hope this helps a little.