You prob'ly should replace the duckbills every few years, but if you run plenty of clean water through it before you remove the hoses, it's nowhere NEAR as bad a job a replacing the impeller in a macerator that's quit working when the tank is full and you're at sea, of course. I think I went at least 6 years without replacing mine, so the pump will still work even long after the duckbills are worn out.