The answer to 'drain replacement frequency' is that there is no single recommended frequency, as it depends on various factors. In general, most plumbers recommend replacing drains every 8-12 years as a preventative measure, or when you notice signs of wear and tear like slow draining, clogs, or leaks. Factors that can affect drain lifespan include the material, usage, and local water quality.
Regularly maintaining your drains through cleaning and inspections can help extend their lifespan. However, it's important to call a professional plumber if you experience recurring issues or suspect the drain needs replacement. They can assess the condition and recommend the best course of action.