You also need to keep your horse the hell away from a barrel pattern except MAYBE one time per week. If I were to train a barrel horse I would do everything I could think off that was not in an arena.
I've had a couple horses that could work on the pattern a couple times a week. Granted, they werent run on it, but they were able to go through and apply the fundamentals without me worrying if they could handle the pressure. I wouldnt RUN a horse on the pattern more than once every week or two. But simple fundamental work wont sour a horse on the pattern.
Now, on the other hand, I've had a horse who wasnt shown the pattern...even at a walk, but maybe once every few weeks.
It's about knowing the individual horse. There is no secret recipe that will be sure fire, bullet proof for every horse. The trick to being successful in this is to KNOW the horse your riding. Know their limits and how far you can push them without them getting fed up.
I had one horse, used to be my main competition horse, who I gave lessons on. He could go through that pattern over, and over, and over again. Never made a peep. Never refused. He had the mind set to be able to handle pressure. Then, after the novice finished her lesson, I could hop on and bring him through without him dropping, dipping, bowing, or tensing. But that was JUST him.
The horse I have now will always turn right around to head back into the arena. Always willing and ready to listen. BUT he still isnt ridden on the pattern often. MAYBE once every few weeks to a month. His problem is that, while he can mentally handle the stress of the pattern, he gets to where he wants to cut corners and cheat me if he rides it often. So schooling the pattern for him is, bring him through...if he does it right... do something else. No repetition on him with the pattern.
Anyway, my point is, its ok to test your horse to see what he can handle... but don't push him passed that limit. Just gotta learn your horse.