Research indicates that the aging process for a roof begins soon after the shingles are installed and progresses rapidly during the initial curing phase of its life cycle. During this stage, granule loss may occur, small blisters may develop, or the shingles may curl slightly at their edges. You may even notice that this curling is more pronounced during cold weather and the shingles may lay flat as temperatures rise. The good news, however, is that after this curing stage the shingles enter a long period of slow aging, which lasts for the major portion of the shingle's natural life.