The frequency of professional fly extermination services depends on the specific needs of your property and the level of infestation. For homes with recurring or persistent fly problems, scheduling regular inspections and treatments (e.g., quarterly or biannually) can help prevent infestations from becoming severe. However, for isolated issues or less severe infestations, a one-time treatment may be sufficient. Consult with a professional exterminator to determine the best approach for your situation.