All systems vary depending on the environment they are in but the more you try to save in not buying a replacement UV Reflector the more you spend in replacement UV Lamps. Most applications it’s a safe practice to replace UV Reflectors every other UV Lamp change as the reflectivity ratio diminishes over time. As a result of being subjected to the direct punishment of a UV Lamp just a ¼ of an inch away @ 650 to 900 degrees centigrade UV reflectors loose their reflectivity.