We would recommend avoiding hand carwashes that use strong alkali detergents (particularly pre-sprays) as these could impact the durability of Rapid Ceramic Spray. The durability of any coating can be impacted by many factors, such as mileage driven, weather, and climate, products used for aftercare and how well the surface was prepared prior to application. If all instructions and recommended guidelines are adhered to, Autoglym Rapid Ceramic Spray will provide up to three months of protection.It is possible, but there is a limited gain from doing so. It is not something we would recommend. On-going cleaning with a Bodywork Shampoo Conditioner and periodic applications of UHD Wax would be more effective. Autoglym does state that Rapid Ceramic Spray lasts up to three months. As with any protection product this time frame is dependent on the environmental conditions, how many miles the car is used for as well as how often it is washed and the quality of the shampoo.