The only time I have ever had to stop was going over a state line, & had to show Coggins, health certificates & brand inspections. Nobody cared where I came from, where I was going to, or how long I had been on the road. On that trip, though I had a an F-250,pulling a 4-horse stock trailer, w 1 small horse & 1 small donkey in it. Coming from CA to AZ, (another trip/but w/only a 1/2 ton) I had all my paperwork , but there was no place that said to stop. Now going into CA is another story-& the Coggins is only good for 6 months not the year most states give you. So taking my new horses back to ride on my favorite trails probably won't happen.
It is always good to have more torque than you need & more stopping power when hauling livestock-they can do crazy things back there in that trailer! And you never know when you will need 4WD! It can really come in handy.