From a Q&A with Linda in the Savvy Club vault, about how long to do a pattern in a given session:
What you have to make sure of is that you are taking care of his Horsenality™. For example, if your horse is a Right-Brain Extrovert you stay on the Pattern until he is calm before you quit. If he is a Right-Brain Introvert, then you wait until he is confident and trusting. This means that there will be quite a bit of repetition if your horse is Right-Brain. If your horse is Left-Brain, there will be less repetition because when he is obedient then you stop.