The answer to 'when to replace drain cleaning' is that you should replace your drain cleaning tools and equipment when they become worn, damaged, or no longer effective. Over time, the cables, blades, and other components of drain cleaning tools can become dull, bent, or corroded, reducing their ability to effectively clear clogs and blockages.
As a general rule, it's a good idea to replace your drain snake or auger every 1-2 years, or more frequently if you use it regularly. You should also replace the blades or cutting heads when they become dull or damaged. Additionally, if you notice that your drain cleaning tools are no longer clearing clogs as effectively as they once did, that's a sign that it's time to replace them.