A persistent morning cough over many years may be caused by post-nasal drip (from allergies or chronic sinus problems), asthma, chronic bronchitis, or acid reflux. You should consult a doctor or pulmonologist for a proper evaluation, which may include a chest X-ray, pulmonary function tests, sinus examination, and allergy assessment. Avoid smoking and exposure to irritants, and consider keeping a symptom diary to help identify triggers and guide appropriate treatment.