Consumer Reports is running long-term tests on more than 30 deck stains to see how well they hold up. The stained panels stay out on Consumer Reports' rooftop for years, in all kinds of weather.
Some are solid stains that look the most like paint. Others are semi-transparent. And a third type, clear sealers, shows the most wood grain. They need the most maintenance; even the best need to be reapplied every year.
Other panels are left out in the shade to see how well they resist dirt and mildew. Again the clear sealers did the worst. Semi-transparent stains do better. They generally need to be redone every two years. Solid stains last the longest. Most last at least three years.
One by Behr was by far the longest-lasting. It's the Solid Color Deck, Fence & Siding Wood Stain from Home Depot. Even after three years of testing, it still looks pretty good.
If you prefer a semi-transparent stain, Consumer Reports recommends another one from Home Depot - Behr Premium Semi-Transparent Weatherproofing Wood Stain.