My dh didn't smoke, but he did chew. We quit together. We had our last smoke/chew together and neither of us has had one since.
My dad and I talked about quitting together, but he quit before I did. He had his last one about 2-3 weeks ago.
I don't spend much time at all with other people who smoke, so that shouldn't be a problem for me. If dh starts chewing again, though, I'm sure I'll start smoking again.