When driving long distances you should not drive any longer than 2 hours without a break of at least 15 to 20 minutes.
I like to stop every 1 hour to 1 hour and 30 minutes to use the restroom, get gasoline, check the oil and stretch my legs and walk around.
I once tried driving for 3 hours straight and my butt was hurting as well as my back and even my legs were going numb.
So always pull over after 2 hours of driving to stretch even if you do not need a restroom break or gasoline although if I'm stopped at a gas station I will top up my gas tank anyway even if it needs only a few gallons.
I figure I'm there at the gas station resting anyway so I might as well add a bit of gasoline to the car so I will not need to stop at another gas station as often.
Driving without a rest longer than 2 hours can cause you to get fatigue and could lead to you having a wreck so always stop for a break.