The answer to 'sewer line replacement frequency' is that most sewer lines last between 50-100 years, but the actual lifespan can vary greatly depending on the material, soil conditions, and maintenance. Older sewer lines made of clay or cast iron typically need to be replaced every 50-60 years, while more modern PVC pipes can last 80-100 years with proper care.
It's important to have your sewer line inspected regularly, especially if you notice any signs of trouble like slow drains, sewage backups, or unusual odors. A professional plumber can use a sewer camera to inspect the line and identify any issues before they become major problems requiring a full replacement.