I'm not sure that it is a progression. Quitting is a process at the end of which you've become an ex-smoker. Being a non-smoker can also be interpreted as a function state .. one who does not smoke. If I'm not smoking, I'm a non-smoker. If I'd never smoked I would be a non-smoker. If I'd given up 20 years ago I'd be a non-smoker. If I gave up yesterday I'd still be a non-smoker:
|Time Quit||Ex smoker||Quitter||Non-smoker|
Most of the table cells make sense, but the question marks are the ones where interpretation is required. Personally I'd say the ? marks should be replaced (left to right) by N, N, Y even though that second N contradicts the previous paragraph. Redefine "Non-smoker" purely functionally as "Non-smoking smoker" and I'd agree with the Y.
I'm still trying to work through going from "Quitting" to "Ex-Smoker". While I wasn't smoking and getting by with Champix, a chemical aid, I was definitely a Quitter. Since then I've been a couple of months not smoking without any chemical assists. Functionally a non-smoker during that time, but with internal turmoil that makes me wonder about my commitment to the process.
The way I model it for myself is that I'm a nicotine / tobacco smoking addict and basically I'm like any other Addict. I happen to be clean and I can usually tell you how many days clean. I have acquired methods and techniques that help me avoid smoking and I have a support network that helps me stay clean. But, beyond all this I am an addict. I am a non-smoking tobacco addict, I don't think I'm really an ex-smoker yet and don't think I have any right to describe myself as that until I realise I go days in a row without thinking about smoking.
That's what I'll say to my fellow quitters. For the last 15 years I've worked with a guy that gave up before I met him. He's told me that he found describing himself as a non-smoker rather than an ex-smoker had one big advantage for him; people didn't offer him cigarettes in the way that they did when he said he was an ex-smoker. I don't know if the 21st century differs greatly from the 20th in this respect, but when talking to a non-quitter that doesn't know me as a smoker I describe myself as a non-smoker and would decline an offered cigarette with a polite "No thanks, I don't"