On rough sawn surfaces look for a lightening in color around flat grain and knot areas. Often times a light tan color develops around the knots. On smooth wood weathering indicators are more subtle
How often you need to reapply a maintenance coat depends on a wide range of variables such as location of the structure, the wood construction, design, etc.
"I used 3 coats of NatureOne® Teak to transform our garage door into a beautiful addition. Thank you Structures."