Most horses can walk all day, but to gallop for very long (hours) is beyond their abilities, and they need time to recover, like any other athlete. That sounds extremely unlikely.
What can you say to a family member who is trying to "keep up with the Joneses" about animal ownership? MIL has told us repeatedly for 8 years that she loves not having a pet to care for, but suddenly decided she needs a certain breed of dog. After doing a little more digging, it is because a woman in the neighborhood has this breed of dog and it is the best thing ever.
MIL doesn't want to buy a puppy from this breed, she wants to find a purebred one to adopt, preferably at no cost. She did go to visit a dog that is mixed breed and has the look of this breed, then decided she must have a purebred dog of this breed.
DH and I are extremely reluctant to encourage her in this, as she does not like animals in her house, this is Florida and it is 90 every day already, and all other dogs she has had were ignored unless it was feeding time or a vet visit. No socialization with other dogs, no walks, no visits to the park. We had to do that to save the dogs from boredom.