On exterior applications on painted metal, Everbrite will need to be reapplied when the surface starts to look dull. Depending on the elements and U.V. exposure, this will be about 5 to 10 years. On homes where awnings or foliage shade the home, only the sides exposed to the sun would need to be refinished. On fiberglass, Everbrite will have to be reapplied every 1 to 3 years. The number of years of protection vary by the intensity of the damaging elements and use of the surface. On brass, copper, bronze, stainless steel etc. the length of time will depend on the usage and elements it is exposed to. On interior applications, the metal will not need re-application of ProtectaClear for many years unless it gets a lot of wear. (For example, copper sinks or counter-tops will need more frequent applications than lamps.)