Mosquito populations fluctuate with the weather, specifically rainfall and temperature. If a dry period is followed by a good rain, you may expect about 12 days later to see a new hatch of mosquitoes. Importantly, these new mosquitoes are hungry for blood – they are not looking for a place to lay eggs, so they are not attracted to the traps. Once they feed, then yes – they are attracted to the traps.
Mosquitoes also travel, typically a couple hundred yards, but possibly more. You may have a nearby mosquito factory, and weather and wind conditions may send them your way. If you can find it, everyone will thank you.
And you can always refresh the trap, even if the nominal period is not up. The rate at which the poisons diminish depends on the temperature, exposure to light, rain that hits the landing pad, etc. Sunlight breaks down the poisons quickly.