I smoked a pack a day from 16 and still smoke cigarettes (over 50 years) and still smoke cigarettes. The last chest x-ray I had about two months ago, looked fine, lungs clear.
I asked, "How can that be"
Doctor said, "You've been lucky, but don't push your luck, you should quit now."
Someday I will... I want to quit.. it's a big waste of money.
But don't use anything I said to start smoking again. You might not be so lucky.
They say it takes about a year for your lungs to be nice and pink again, but the healing starts as soon as you quit, after your last cigarette.