55-75 mph or whatever the max speed is and if I have a need or feel like traveling at those speeds.
I see rv transport rigs on I-44 daily near me doing 75-78 mph with someones new RV trailer.
We just got back off a 2700 mile trip out west in september. Coming towards home on I-80 in WY and I-70 in CO/KS...... had lots of trucks pulling rv trailers doing the max speed limit +.
Some folks and certain rigs shouldn't pull that fast.