I would find other things I'd rather spend time doing (working, studying, etc.) during most of the time they are smoking. Presumably they spend a goodly bit of time smoking and not doing much else? I'd get away from that. It might be helpful to you if your bf had smoked but wasn't actively smoking when you are with him?

It will make you "cross" to not smoke, maybe even a bit depressed, you will get little aches and pains and out of sorts (people who are tested in labs, trying to give it up for a week, often leave before the experiment is up and blame the bed pillow for being too hard/soft or some little thing like that, never that they really miss the smoking).