Window manufacturers recommend having your windows cleaned every 6 months. Regular cleaning prevents your windows from permanent damage that can be caused by saltwater, oxidation,acid rain, pollution, overspray, pesticides, rust,calcium, mold,bird/lizard droppings and other elements that windows are exposed to daily. It also removes allergens such as pollen that tend to stick to your windows. Homes on the water (salt), or near high traffic or construction should consider quarterly service.