Does Your FenceActually Need Staining?

Cedar weathers to a silver grey on its own within a season or two, and that's fine left alone if you like the look. If you want the warm color to stay, it needs sealing. Pine needs longer still before it will take stain at all, so timing matters more there than it does with cedar. Vinyl and aluminum need neither, no paint, no stain, no sealing. The coating on aluminum is there for the color rather than for protection, so there is no rust to stay ahead of the way there is on steel left unmaintained.

Give the wood a couple of months to dry out and settle first, then seal it inside that first year if you want to hold the color, before it's had a chance to grey. Sealing a board that is still wet from the yard just means the finish will not take. Beyond that first year, how often it needs redoing depends on the product used, sun exposure, and how much of the color you want to keep, which varies enough by property that a single interval isn't honest to state here.