A variety of factors can affect shingle life, including weather, roof pitch, quality of installation, and of course the quality of the shingle. Shop around and you will find warranties ranging from 15 to 30 years. Here in southern California, where we do not have the issues with ice dams, algae, and spiking temperatures that other regions do, you can expect your shingles to reach the upper end of whatever lifespan the manufacturer promises for them.