Fluorescent bulbs need to be replaced every year as they naturally degrade and lose about 40% UV light output, resulting in decreased fly catch speed and performance. Comparatively, LED bulbs have a 3x longer lifespan.

Fluorescent UVA bulbs that have crossed the one-year mark do not stop attracting flying insects. It is just that their performance deteriorates with time. It may be beneficial to change the bulbs more frequently in tropical climates since they have a less-defined fly season. Whereas for temperate climates, it is recommended to replace the bulbs in spring.