To keep things in perspective most of the plywood in a transom or on a floor has had minimal or no treatment coming from the factory, so in many cases this has lasted 25, 30 years or more unless there was some sort of breach, something spilled on it, or something drilled through and not sealed. Therefore as I mentioned above taking the minimal steps to improve things as part of the replacement is going to last perhaps 35 or 40 years. But again, a lot of material choices to ponder.