Disease in early stage, Start treatment immediately
Immediate effects could be happened, and could cure in short term. Mostly, Qi energy blockages are cause. (In this case, western medical point of view, medical doctors would say, "There are no causes we could find.") Sometimes, due to overdid or so, temporarily physical status get worse, but it is easy to recover by treatment.
General (Moderate) Cases
There are two curves; one is steep (recovering period), the other is gentle (plateau period). Of the steep part, you recover dramatically, while in gentle part, you may not feel it so much. Hence, many patients feel that they do not become better while they are in plateau period. Usually, recovering period and plateau period comes alternately, and overall, patients are getting better. The red line shows that he/she recovers so well, so they behave as they used to be. Hence, they start feeling pain again or treatment effects decreased. However, it is rare to back to the condition of before treatment started.
Serious diseases or long illnesses
It has long gentle curve (plateau period). Basically, it requires as the same period of time as you have been in illness. There are not only Qi energy blockages; in addition, there are severe static blood created in this case.
Of course, it does not follow above curves, always. Of some cases, there are possibilities to recover, suddenly. For example, frozen shoulder is so. It takes at least 3 months, but if you don't give up treatment, it would be suddenly gone. Paralysis is the same.
Also, period of plateau is different in each patient. Some are two weeks, and some are several months. Long illnesses patients tend to have long plateau period as you may think so. However, if patients don't give up having treatment, then suddenly recovering period comes again. (Unfortunately, many patients give up before they face recovering period. Especially, Japanese patients tend to do so.)