Ultimately, overapplication of stain can compromise the deck's appearance, durability, and longevity. It may result in an uneven finish, with excess stain pooling, dripping, or drying into thick patches. It can also obscure the wood's natural grain and texture, detracting from the desired aesthetic. Moreover, excessive staining may not fully penetrate the wood, leading to poor adhesion and premature wear. Additionally, thick layers of stain are prone to peeling, cracking, and blistering as they struggle to bond with the surface. 

Applying a sealer or topcoat after staining wood is highly recommended, though not always strictly required. A sealer protects the wood from moisture, UV rays, and weather-related issues, which is especially important for outdoor surfaces like decks and fences. It also enhances the stain's durability, prevents fading over time, and gives the wood a cleaner, more professional-looking finish. For some indoor applications, a sealer may not be necessary, depending on the type of stain used and the level of protection needed. It's always best to check the stain manufacturer's recommendations and consider the wood's intended use and exposure when deciding whether to apply a sealer.

Wood stains last anywhere from two to five years, depending on exposure to the elements, your local climate, the type of stain, and the surface it’s on. For instance, vertical surfaces last longer than horizontal surfaces. Some types of woods, like dense hardwoods, will require a recoat yearly, as they are too dense for the stain to absorb. In any event, apply a recoat every 2 to 4 years. As for storage, a can of unopened stain can last up to 5 years, though results may vary.

Yes, staining or sealing a cedar deck or fence is highly recommended to extend its lifespan, typically by five to 10 years. While cedar is naturally resistant to mold and mildew, it can still fall victim to moisture, sun exposure, and rot over time. Applying a treatment creates a protective shield that helps prevent splintering, fading, and decay, preserving the wood's strength and appearance. A combination stain and sealer often provides the best protection, as it soaks into the wood grain rather than just sitting on top. This offers superior defense against UV damage and rot and lasts longer than a sealer alone. To maintain the wood's natural look, consider using a near-translucent stain. You should plan to reapply the stain or sealer every two to three years.