Maintaining the UV protective topcoat is the key to keeping your outdoor wood project looking like new for years to come.
Estimating the longevity of any finish in an exterior environment is difficult to determine. The deterioration rate is heavily dependent on the severity of exposure and the intensity of exposure can drastically differ from location to location.
Another big factor is the preparation of the wood. The wood should be dry with a sufficient film build of epoxy encapsulating it (top, bottom, sides, edges, corners). The Marine Spar Varnish protects the epoxy and the epoxy protects the wood. When the varnish starts to dull, lightly sand and apply a fresh coat to refresh the UV absorbers. Provided the conditions above are met and the varnish is properly maintained, theoretically, the epoxy and wood will be protected indefinitely.
Maintenance of the varnish is also difficult to estimate. Re-coating the varnish can be needed every 1-2 years in the most extreme equatorial and sunny environments. In higher latitude, shadier environments, you could get as much as 5 years. Please read through our Clear Finishing of Outdoor Wood Guide to determine if your project is a good candidate for our system.