The owner of the dog needs to know how to "operate" the dog, same way you can get into a car that's in perfect running order but if you don't know how to drive you won't have much luck making the car go anywhere. If the owner doesn't know how to maintain the training, the dog will soon become untrained again. Read more here
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People seem to think that once a dog is trained, that's it. Not true. You must reinforce the dog's training every single day in some way. It's best if the owner and the dog go together to get trained. As a professional trainer once said to me "We can train any dog in 2 days. It takes longer to train the owners