Yes, it is generally a very good idea to seal your deck after pressure washing. Power washing removes not only dirt and debris but also a thin layer of wood, leaving the surface exposed and more susceptible to weathering. Sealing is almost always needed after this process. After a general cleaning, sealing isn't automatically necessary if the existing sealant is still intact. You can test the surface by placing a few drops of water on it. If the water beads up, the sealant is working. If it soaks into the wood, it's time to apply a new sealant. If it has been a few years, it's wise to remove the old sealant, wash the deck, and reseal for maximum protection.

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. 

Staining or sealing a cedar deck or fence is highly recommended to extend its lifespan and protect it from the elements. While cedar is naturally resistant to mold and mildew, it is not impervious to damage from moisture, sun exposure, splintering, fading, and rot over time. Applying a protective finish creates a shield that preserves the wood's strength and appearance, potentially extending its life by five to 10 years.

When choosing a finish, it's helpful to understand the difference between a sealer and a stain. A sealer sits on top of the wood, whereas a combination stain and sealer soaks into the top layer. Because it penetrates the wood, a stain generally offers better protection against UV damage and rot and lasts significantly longer. For the best results that also preserve the wood's natural color, consider using a near-translucent stain.

To maintain protection, plan on reapplying the stain or sealer every two to three years, either as a DIY project or by hiring a professional.

There are deck restoration products and oil-based wood stains that can help bring back some of the color and shine to your faded Trex decking. However, if your boards are suffering from serious fading due to UV rays or chemical cleaning products, don’t expect miracles. Also, these products are only suitable for use on the older Trex boards, not the capped, second-generation Trex products.