Ask a PT Response: "With custom orthotics, it is recommended that they be utilized as much as possible. When orthotics are utilized, the user's body must become accustomed to the postural and biomechanical changes that are often associated with orthotic use. Therefore, it is generally recommended to gradually build up the time of use in the beginning to the point where they should be utilized as much as possible. Intermittent use will most likely not yield the most optimal results and require the body to frequently become accustomed to the orthotics. In your case with shin splints, if the inserts on helping than I would continue with there use. However, often times there are other contributory factors besides foot structure which may be playing a role in the development of shin splints as well ie. weakness, flexibility issues, joint mobility issues, poor running mechanics, etc."