You should inspect your sewer line every 3 to 5 years. This will help to ensure any potential issues are identified and addressed before they become a major problem. It is also a good idea to have it inspected if you experience any signs of potential problems such as large tree roots in your yard, bad odors, slow drainage, or frequent clogging. Professional plumbers have access to larger bore snakes and augers and can pinpoint any issues that may be present in your sewer line. They can also provide advice and periodic resnaking services.