does it matter what time you feed your horse, just so the feedings are at the same time every day?
There's a difference between stable horses, work horses, pack horses, ranch horses, and rodeo horses.
Stable horses can get idiot riders that don't know straight up about horses and make all sorts of bad mistakes. They are used to exploiting those mistakes and can get really spoiled. They put on too much fat and get hoof problems (laminitis) as the result.
Pack horses (sometimes work horses) go on longer trips but they usually know where they are going and will continue to the next feed station and stop there for a good feed. If no one is there they want to go to the next station that might be a day's ride away. You will have to tie them hard to get them not to leave if you don't feed them on time.
Pack horses figure on going anywhere their master tells them but if a stranger is riding them they will make the rider prove his mettle. Once the horse is sure of the rider he will go nearly anywhere . . . well, I said NEARLY anywhere. They want to eat dawn and dusk and you had best be ready to give them good pasture or good hay when you get there.
Ranch horses know every inch of the ranch and can get you from point A to B without you much more than making it clear by your guide where you want to go. If you have a cutting horse, he will never want to leave the remuda or corral. If you have a range horse he can't stand that remuda or corral and will let you know about it -- big time. Either way they still want to eat on schedule.
Rodeo horses are a little like wild broom tails in that they will kill you if they get half a chance. If there was a prison for horses they would be in it. Rodeo horses are supposed to be miserable to ride so you don't feed them on schedule. You might feed them 3 or 4 times a day just to keep them rowdy and nasty but you don't stick to any specified schedule.
Adjust your feed schedule accordingly.