How often does the nozzle require changing on the Riello 40 Series F3 burner? My furnace is approximately 10 years old, and to the best of my knowledge the nozzle has never been changed. The furnace is working fine at present, and fuel consumption is acceptable. There are no issues at present, but I would like to know the recommended service/replacement intervals so I can have proper preventative maintenance performed if/when required. Thank you in advance for your assistance with my inquiry.