On decks and horizontal surfaces, Behr premium transparent wood finish lasts up to 6 months before needing to reapply. On fences, siding, railings and other vertical surfaces, it can last up to 2 years when applied properly. To maintain the protective barrier, it's recommended to recoat every 6 months to 2 years depending on the location. With regular reapplication, Behr wood finish can provide decades of protection for exterior wood projects.