How often should I change out the cartridges?

Hi, Dee. We recommend that you replace the Zevo Trap refill cartridge when it is full of insects, which you can check every 2 weeks or as needed. We have created Zevo Flying Insect Traps with a unique tab feature so you can lift the cartridge and check how many bugs you've caught without making a mess and without touching the bugs. Use your thumb and index finger to squeeze the tab on top of the cartridge. Pull up gently; you will see that the blue light turns off. When you are finished, simply push the cartridge back down and you will see the blue light come back on. We hope this is helpful, but feel free to give us a call at (866) 215-1297 if you have any other questions!