I shipped my horse from PA to AZ when he was 20. I used a commercial shipper out of Colorado Springs, All State Horse Transport. Air ride in a normal stall right next to the box stall where there was a scared weanling that he baby-sat all the way to CO.
(Off topic, but I was just so proud of him: The drivers said my horse was a godsend. The weanling, newly weaned , was picked up in NJ and screamed the whole way to western PA, wouldn’t eat or drink. My guy was the next horse loaded and immediately reached over and touched the weanling’s nose. The weanling instantaneously calmed down and started eating hay. At that point, my horse decided it was his job to make sure the baby was okay. They tied him so he could continue to reach down to the baby, and they were both happy as clams).
Back on topic: They stopped a couple of times between PA and CO at farms with separate grassy paddocks where they could stretch their legs for 3-4 hours. Other than that, they drove straight through. They called me every day from the road with an update on where they were and how he was doing.
He was then at the home farm in CO for 4 days waiting for a load for the Southwest. The office personnel there (all horse owners) loved him. (I’ll admit he was Mr. Personality Plus. ). They would go out to the stalls, feed him carrots and call me with an update every day.
He arrived in AZ bright-eyed and in good condition. He was an OTTB, so he did drop a little weight which I had expected. He was a busy-body type who found everything more interesting than his food.
I transported this same horse 1000 miles when he was 30, and he did great then, also. All that to say, if the horse is relatively healthy, there shouldn’t be a problem no matter the age.