The answer to 'when to replace shingles' is that you typically need to replace asphalt shingles every 15-20 years, or sooner if they show significant wear and damage. Shingles can become cracked, curled, or missing over time due to weather exposure, and this can lead to leaks and water damage if not addressed.
Signs it's time to replace your shingles include extensive cracking, missing granules, curling at the edges, and visible wear. You should also replace shingles if you notice leaks in your roof or significant damage after a major storm. Replacing shingles before they fail completely can help prevent costly water damage to your home.