Towing speed?

58-63mph seems to be real easy going.. sometimes 65, it depends on situation. 60mph is speed limit for towing travel trailers in Washington I am told (need to find that RCW one of these days for fun)..

What are your tires rated for?
Is your setup well maintained?
Do you do safety checks?
How does your rig handle?
Do you care about mpg at all?
What speed is traffic moving?
How many lanes, are you holding up traffic?
.. and so on... really depends on your risk level.