While acupuncture is an amazing and often effective medicine, everyone's response to it will be different depending on factors like age, how long the condition has been present, and overall health and vitality.
There are many times where symptoms are alleviated within 1-2 treatments, but overall it is important to be realistic with expectations. To expect to be fully healed from 25 year old chronic pain in one treatment is like believing you can go to the gym one time and look like a bodybuilder. It's probably not going to happen.
The article linked above does a wonderful job using charts to outline the recommended frequency of treatment and how symptoms are their severity are reduced over a fairly short period of time. Of course life can get in the way from time to time, but doing your best to stay on your course of treatment will get you feeling better faster and create longer lasting results and healing.
Click the picture above to read the article.