Copper roofs can last from 60 to over 100 years, making copper one of the most durable roofing options available. The lifespan of a properly installed copper roof primarily depends on the amount of water it is exposed to, as well as the thickness and hardness of the copper material. While copper roofs develop a protective coating, the green oxidized patina seen on old copper roofs can be worn away by water running consistently over the surface, which can then erode the copper metal. At about 60 years of age, copper roofing will develop pinholes below slate and tile roofs, where water tends to drip repeatedly onto one area of copper. Copper valley flashings will wear through the center of the valley, near the lower end of the valley. Long roof valleys will wear through sooner than short valleys as they carry more water. Copper roofing will also wear through at the edge of parallel folded or lapped seams. Copper roofing and flashings are also adversely affected by acidic tannins leaching from some cedar and oak tree species.