My mom has nearly quit smoking, though not by choice -- she was hospitalized for nine days and on a no food, no liquid diet (except for occasional ice chips) for 85% of that. As a result, when she was released from the hospital, she had gone through over 9 days without a cigarette and without being around smokers. Her smoking has been drastically reduced since her return home.
I must say, I do not recommend having to be transported by ambulance and hospitalized for 9 days as a means to quit smoking, but that is how it worked out in Moms case. Incidentally, she was hospitalized for something wholly unrelated to smoking -- pancreatitis (NOT pleasant; best guess is her rheumatoid arthritis medication may have triggered it, as pancreatitis is one of the myriad potential side-effects.)
Dad has quit smoking at home, but I am not certain he has quit smoking at work (lunch hour, etc.) and when driving. That said, whenever I visit them I do not find him missing for over-long.
My brother and I never smoked, but we were around two heavy smokers (Mom and Dad) from early childhood. For parents who think cracking a window in the car spares the kids the second-hand smoke, all I can say is -- it doesn't. I couldn't even hazard a guess on what my lifetime exposure to
second-hand smoke has been. I was a severe asthmatic as a child, and I have allergies as an adult (including to cigarette smoke), though I don't attribute second-hand smoke to these things it certainly doesn't HELP.