It depends on the disease. If it is an acute condition like allergy, infection, etc. you do not need to take long term medication.
But if you are taking homoeopathic treatment for chronic diseases like diabetes, chronic joint pain, heart disease, blood pressure, PCOD, thyroid conditions, etc., then you would need to take medication for a slightly prolonged time.
If you are having that disease/symptom for a long period of a few months/years, then you cannot expect that it should go away quickly.
But Homoeopathy will definitely show positive effects gradually and will help to treat the root cause of your problem, in a natural, gentle and holistic way