Well, no guarantees. First of all, even though we all keep finding things in common, nobody's situation is really the same as anyone else's, and although I think everyone here does it, looking at others and assigning yourself a time frame for success is a mistake.
That said, I guess it depends on your definition of progress, but certainly you could see progress in 6 months. You will not go from a long-term sex-starved marriage to a happy, well-balanced sex life in six months, though. On the other hand, moments that wouldn't seem like much to anyone else can be big boosts when you're used to an SSM.
I came to the forum about the same time I confronted my wife for the hundredth time and got blown off in a flood of tears, then started a sabbatical from all sexual activity (well, attempts) as per the SSM book. Not long after, I gave her an ultimatum: work on the marriage with me or we're headed for a divorce. That came out of my discussions here.
It only took a month or so to get to a point where we were talking very honestly about sex and love (despite her tears, which had always stopped me before) and trying to make love once a week. Sometimes that was great, sometimes it was awkward, but it was a hundred times better than the previous few years of making love once every one or two months. And I was beginning to get back into my old hobbies and some other things I'd given up in the marriage, because in my particular case I have some "Nice Guy" tendencies (there's a book on that, too, called "No More Mr. Nice Guy.") Eventually, we reached a point where she now tries to be open to sex, and we sometimes have it two or three times a week. More than that, I'm taking more control of my life, taking more of a lead in our relationship, and working toward my own goals. The more of this I do, the easier it gets to work together on our sex life. She's trying to do the same. We took a ballroom dancing class together, I'm doing some writing, she's taking some kind of weird dance-aerobic classes, and I'm making real progress on our old house rehab project.
It all feels good. But is our marriage fixed? Not really. For one thing, if we go too long without sex of some kind, I still get edgy and start thinking about her backsliding and going back to SSM. We had fantastic, mind-blowing sex ten days ago, but that was ten days ago, and right now I'm fighting the return of all those old feelings of anger and rejection. If you'd told me a few years ago that I could have the best sex of my life every ten days, I'd have asked where to sign, so I have to keep things in perspective. In the past, I've gone over a year without any sexual gesture from her at all. She's not perfect today, and neither am I, but now I know for sure that we're trying, and that makes all the difference. What I was trying to get across to Young at Heart is that as you contemplate fixing a sex-starved marriage, you think there's no way you can stick through it to the end. You don't account for the way your mindset will change when you have some positive things to think about.
It's been two years for me, but it hasn't been two years of the kind of rejection and fury and sick anger and hopelessness that I had years of before. It's doable.