The answer to 'how long does shingle replacement last' is that asphalt shingle roofs typically last 15-30 years, depending on factors like climate, roof slope, and proper installation. Properly maintained asphalt shingle roofs can last on the longer end of that range, while roofs exposed to harsh weather conditions may need replacement sooner.
Shingles can start to show signs of wear like curling, cracking, or loss of granules over time. When 20-30% of the shingles are damaged, it's generally time to consider a full roof replacement. Calling in a professional roofer to inspect the roof and provide recommendations is the best way to determine if and when a replacement is needed.