There are a few factors that determine this. It depends on the state of the body, what the condition is, its severity and how long the condition has been affecting one's life.
It depends on whether the person is complimenting the herbal regimen with vitamins, minerals and a reasonably healthy diet while eliminating the antagonist. One example would be if someone is trying to rejuvenate one’s liver with a liver herb but continues to consume alcohol excessively and/or consistently eat sugar the process of seeing positive results can take much longer/if at all to see the positive results they are looking for. But on the other hand, if one removes the antagonist, supplements appropriately and adopts a healthy regimen, benefits can be noticed within a week and in some cases as early as a day. Again this all depends on the individual and their respective situation combined with one’s own will to make more constructive choices.