Honestly, man, and I don't mean to make you feel bad, but this is the stupidest thing that I have ever heard of in my life. I pray at night that people like you will not have children.
To answer your question, and taking into account that the time it takes will vary from person to person, I would say that it takes longer than you might expect, but not very long in the scheme of things.
For example, I began smoking two or three cigarettes a day, and I thought, "Well hey, this isn't so bad!" I smoked maybe two or three cigarettes a day for over a year, but then I began smoking four or five cigarettes a day. I couldn't walk by someone smoking without wanting to smoke as well. It's a strange thing.
I don't smoke anymore, but even still, I find that it's hard to be around someone who's smoking without wanting to light one up myself.
