So, this afternoon, my Wife/KH and I were discussing me giving up smoking. I casually suggested that it might be a good idea to unlock me during this time to reduce irritability. She just looked me square in the eye and told me the only way I'm ever getting out without her supervision is to use my safeword. Up until that moment, we've just sort of been fooling with chastity but I'm thinking now, shit just got real...
She could go a step further and say you aren't going to be unlocked until you have been smoke free for 100 days, or something like that! (If you can go three months without a cigarette you will probably be able to go longer.)
May KH routinely uses (or tries to) chastity to try to help me break the many bad habits and various vices I indulge. Depending on the habit and her commitment it could probably work. Punishments for indulging have to be sufficient to deter. She's had some limited success, at least for a period of time, with some of my habits. So I'd imagine so could yours.