Here comes my dreaded answer - It depends.
Each disease has its own path, and all can be serious. And, as far as I know, none is curable except in some cases chronic bronchitis, if the trigger is found and removed before you progress to other issues.
The problem with emphysema is that it typically occurs in lungs already compromised by smoking or another irritant and because the person already has a cough, the increasing severity and shortness of breath may be ignored until the disease is well progressed, and halting progressive damage is difficult.
There are people who have chronic bronchitis (inflammation of the airways) for many years without progression to emphysema or another disease.
Then there those of us with bronchiectasis, which can be mild, moderate or severe, and stable or progressive - often depending on our ability to avoid infection. Or other diseases that share our lungs. Some, like my Mom, have it for many years and die in their 80's of other causes. Others may have such progression as to need lobes removed, or even a lung transplant.

Sue