I tow a 30' TT and run 55, slower if it's windy. Avoid interstates like the plague, but sometime's they're necessary. I stay in the right lane and don't impede traffic. If I'm on a two laner and traffic starts backing up behind me and they can't pass, I will find a safe place to pull off and let them around.
There are a plethora of areas in my life where I'm in a constant Hell-Fired hurry by necessity.....RVing isn't one of them. It's the time I relax and decompress, and my driving reflects that. Plus my feeling is that if something goes wrong at 55, I can probably gather it back up or at least minimize damage or the potential for injury. At 70, maybe not. Plus I pick up about 1 mpg by going slower. And what's the cost....I get there an hour later? Big deal.