So, the true answer is that I cannot know the future, but I do know that it will be helpful for you most likely and that it will keep getting better longer or, if you are one of those "miracle patients," it may stay well for a good long time.
Hope that answers your question.
With pain patients, a lot depends on how long you've been experiencing the pain and how severe the pain currently is. A typical course of therapy might be 5-7 treatments spaced 1 week apart followed by increasing the time between treatments until some maintenance interval is found which gives you sufficient pain relief.
The maintenance interval is mostly an individual thing. I've had patients whose interval was monthly and patients who came to see me twice a year after we got their issue under control.
When you start seeing an acupuncturist, expect a little up and down in your pain levels as you progress. Typically my patients experience a sharp reduction in pain after the first or second treatment. This initial reduction will last a day or two and then the pain returns. Each subsequent treatment reduces the pain a little more and/or extends the time for which the pain is either relieved or reduced. When the patient can go 5-7 days with either no or minimal pain, then we start to space the treatments out.