Use the manufacturer's schedule for the exact unit and its actual conditions. There is no single interval that should be imposed on every wastewater product.
What the observation means
Water hardness, use and approved maintenance arrangements can differ. A calendar reminder does not establish that a present fault is only scale.
A useful next step
Keep a record of the permitted product and dates used. If running, drainage or leakage changes, arrange assessment rather than bringing the next treatment forward repeatedly. Do not exceed the instructions or substitute a stronger chemical based on general hard-water advice.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.