Welcome to the forum madhatter. You are correct. A support group is one of the elements that aids in your recovery. It is not a requirement but it surely helps. Your post seems to lean heavily on the idea that your success is all left to chance and you speak of a "window of opportunity" as though you are not at all in control of your own destiny. I want to assure you that you are and I want to convince you that you have already succeeded, you have quit.
There really is no luck involved. You may consider finding this site luck but you made the effort, you came looking for answers. Don't now sit there and wait - Be proactive. Learn about your addiction. It is knowledge of what you are about to face as you learn to live without nicotine that will help you to face the challenges associated with this period of readjustment. I encourage you to read as much as time allows. There are many here who smoked longer and harder than you and have quit just the same. It does not matter how much nicotine you used or even how you got it into your blood stream, it only matters that you now want to remain nicotine free. You have come to recognize that your addiction to nicotine has begun to affect your life in ways that are unacceptable to you. We are here to assure you that you have within you the ability to remain nicotine free by following one simple rule - Never take another puff.
Be proud not hesitant. You are not practicing or making a trial run. This is it. You HAVE quit.
Joseph
2 years, 10 months