The answer to 'how long does drain last' is that the lifespan of a drain can vary widely, but typically a well-maintained drain can last 20-40 years or more. The actual lifespan depends on factors like the material the drain is made of, the amount of use it gets, and how well it is maintained.
Drains made of PVC or metal pipes tend to last the longest, often 30-40 years or more with proper care. Drains made of older materials like galvanized steel or cast iron may only last 20-30 years before needing replacement. Regular cleaning, avoiding pouring harsh chemicals down the drain, and promptly addressing any clogs or leaks can help maximize the lifespan of a drain.