How long can emphysema last?

Life long. Once you have emphysema, it will always be there. Once you lose lung tissue, it is gone forever. That doesn't mean life is over...There are very good treatments, and people with emphysema can life full, productive lives. Best thing is to stop smoking and see a doctor to get treated.
Lifelong... Emphysema, a form of copd, is a slowly progressive disease that has no cure. Treatment includes bronchodilator and steroid inhalers as well as oxygen, if the oxygen level is low enough to warrant it. There is no cure so, once present, it is a life-long problem. Smoking cessation is necessary to decrease chronic airway inflammation. See your doctor so the diagnosis can be made and treatment given.
WON'T LAST. Lets review the simple definition of emphysema: an abnormal permanent enlargement of air spaces with destruction of alveolar walls. As you see it is a permanent damage. You just have to control that and prevent aggravation.
Forever. Once the condition is causing symptoms that are severe enough for a doctor to diagnose emphysema that means that there is a lot of lung tissue that is scarred. The scarring is permanent and there is no medication to reverse it. The medications to treat emphysema only help the remaining unscarred lung tissue to work better.