The rule of thumb for applying multi-season antifouling paints (including TotalBoat Spartan) is one full coat per season of use, at a bare minimum, with additional paint in the higher wear areas (such as the leading edge of keels, rudders, or skegs, the very bow, and along the waterline of a boat). For areas that do not exhibit a lot of growth, it may be possible to stretch a coat of paint for two years, with some touch-up in heavy wear areas, but it's strongly recommended to apply at least one full coat of paint per season of use to ensure sufficient antifouling performance.