I would think your driving tolerance could be based on your occupation, or previous occupation. If you drive/drove for a living, I would understand driving further without feeling complete exhaustion. People with more sedentary lifestyles, or short commutes, wouldn't handle several hours in the vehicle very well.
I myself drive for a living, truck and trailer locally. I used to drive 7-8hrs one way every other weekend to visit with my wife, so the long trips aren't as draining to me. I made that 7-8hr many times without even stopping once. My TDI Jetta could go upwards of 600mi without a fillup.