A single stem cell treatment can result in clinical improvements that might last for several years, depending on the specific health issue. For instance, in cases of joint treatments, we've observed the growth of connective tissue for as long as 6 months after the cell injection. When it comes to autoimmune diseases, the level of symptom control achieved can extend up to a year following intravenous application, depending on the seriousness of the condition. However, it's important to remember that even though stem cell therapy holds great promise, the exact effects in each individual case cannot be guaranteed.