I've been smoke free for over 150 days but, I haven't noticed any positive changes. I never coughed up brown or black flem. I always ran and smoked while in the Air Force for 20 years. I only change I experienced is my daily glucose numbers rose after I quit and they should remain higher than normal for up to three years from what I have read. I have had to inject more insulin and have gained 40 pounds in six weeks due to the increase of insulin at each meal and when I inject the long acting insulin twice a day. I do not see a valid benefit to quitting after being smoke free over 150 days.