I take my GPS on all my rides and have been tracking this for some time.
My wife and I, me on a gaited horse and her on a quarter horse, usually average between 3.5 and 4 mph, average moving time.
What this means is an 8 mile loop is finished in about two hours.
I most always take a map and compass, and in addition to my GPS, my wife also takes a GPS as well. My gaited horse will always show more mileage as I'm constantly getting well in front of her, and then riding back to her. Sometimes I ride circles around her.
For we wrestle not against flesh and blood, but against principalities, against powers, against the rulers of the darkness of this world, against spiritual wickedness in high places.