Asphalt roofs don't last forever. Even if they aren't damaged by a storm or raccoons, old age will take its toll eventually. The granules shed as the roof ages, and exposure to wind, rain, and UV rays will gradually wear the shingles down. Knowing this, it's best to plan for a roof replacement before your roof is so old and worn out that it leaks. Here are some reasons to schedule a roof replacement well before problems develop.