The answer to 'when to replace shingle replacement' is that asphalt shingle roofs typically need to be replaced every 15-25 years, depending on factors like weather, roof slope, and quality of installation. Signs it's time to replace shingles include curling, cracking, missing granules, and leaks. Replacing shingles before major damage occurs can help prevent costly repairs and extend the life of your roof.
It's best to have a professional roofing contractor inspect your roof every 5-10 years to assess its condition and recommend whether replacement is needed. They can also advise on the best shingle type and installation methods for your home.