Anything above 7 days could cause rebound effects, and he must see a doctor regarding how to solve the symptoms caused by the nose spray.
Side effects are nasal congestion, other nose problems and as a matter of fact, high blood pressure.
If he is short of breath, self-medication with nose spray is not good. The doctor must find a cause (unless the only symptom is nasal congestion, that would likely be caused by the mentioned side effects).