The amount of years that quitting smoking can add to your life will depend on how old you're when stopping smoking.
If you quit smoking at age 20 you extend your life by at least 20 to 30 years but if you're 60 or above then you can still extend your life by 10 to 20 years or more.
Giving up smoking cigarettes is the best thing you can do to add years to your life and help improve your health and prevent yourself from developing lung cancer, lung disease and COPD as well as heart disease.
For those that are thinking of smoking you should not smoke as it decreases your life expectancy and makes it hard for you to breath later on in life and might require you to get on oxygen.