I don't drive any type of RV at 70 consistently no matter if I am towing or not. They may "feel" solid and safe at those higher speeds but they certainly do not stop on a dime plus if you ever swerve or blow out a front tire you will wish you were going slower.
That being said, most speed restrictions on equipment is due to tires. If you run cheaper lighter duty tires above their speed rating, especially in very warm conditions, they heat up, air pressure increases, and blam!
Full Time in 2017 Newmar Ventana 4369
pulling a 24' enclosed (Mini Cooper/Harley/Kayak)
(traded 2014 Thor Challenger)
US Army 70-73 Retired LEO