I built a 14 ft kayak using 4 mm marine plywood, one layer of fiberglass, epoxy, and then varnished. If I store it inside out of the sun and minimize the rock damage how long will the finish last ? I read after 5 years it must be sanded and re-varnished but the article didn't specify if that was for larger wooden boats stored in the sun and or in the water. Also, what is the chance of rot occurring ? Since this was my first boat I have sealed spots where the glass did not lay perfectly.