Plastic boats most often die of ultraviolet (UV) light exposure. If you leave it in the sun long enough the UV protection in the plastic will give out and the boat will oxidize and become brittle. So wax is nice because it makes the boat slippery and shiny. But wax with lots of extra UV blockers is nicer still. The usual recommendation is to go to a boat yard and get a good marine wax. Or if you are lazy get some 303. It goes on very fast (spray on with no buffing) but then also washes off fairly fast (darn).

David