Brief Answer : In healthy adult cases about 2-3 weeks. Detailed Answer : Hello! I have read carefully you concerns. Pneumonia is as severe inflammatory condition of the lungs. For how long this condition last it depends on different factors. First, in people who are older, or people who suffer from any other chronic condition, pneumonia tend to last longer, and may have more severe symptomes. From the other hand, younger people, are more often to have mild symptoms and the condition last less. Also the etiology of pneumonia affect the prognosis of the desease. Usually viral pneumonia is less severe and tend to last less than bacterial penumonia. If you have a strong/healthy immune system, the chances of fast improvments are higher. But if after a couple of weeks, you see no improvments, your cough is worsening, you have fever, and chest pain. You should do an X Ray and check with your pneumologist, because you might need a stronger course of antibiotics. Please feel free to ask again if you have any other question. Take care!