I quite cold turkey in 2001. Hubby "quit" at the same time...cost prohibitive. I'd say smoking is cost prohibitive when you're charging them on a credit card. Blech. Hubby never really quit though. He would bum smokes at work and buy a pack every now and then. But we got back on our feet after a rough spell and I never picked up the habit again. He smoked less than I did anyway (less than a pack a day) so it wasn't a huge cost for him to continue.
Best I could do was to never be around smoke. So he started smoking outside. Since he couldn't give it up, the least he could do was be a bit accomodating to me since I was working so hard at it. I also kept lots of gum on hand. And I vowed to never even dare take a puff off someone's smoke, no matter how bad I started wanting it. Instead, I'd have to walk away.
Do things together to keep him busy, keep his mind occupied. But keep him away from areas where there is going to be smoke. IE: Go to the movies and not to the bars.