The duration of clean windows largely depends on environmental factors, such as weather conditions, proximity to sprinklers which can deposit hard water spots, pollinating plants, etc. On average, professionally cleaned windows might retain their cleanliness for about three to six months before needing another cleaning, while windows in areas that experience more inclement conditions may benefit from more frequent cleanings. Factors like heavy rainfall, wind-blown debris, and nearby construction can diminish the longevity of clean windows. Routine maintenance, such as regular dusting and occasional spot cleaning, can extend the time between professional cleanings. Furthermore, high-quality window treatments and protective coatings can help shield windows from dirt and grime, prolonging their cleanliness over time.