Mosquito Eliminator Disks

I got these at the beginning of the summer and hung one on the front door knob. We had fewer mosquitoes get in the house this year. It seems that since they aren’t hanging out right at the door they don’t slip in as we go in and out.
Haven’t tested how they do in a more mobile situation.

Any idea what kind of coverage these have, or how long they remain at maximum effectiveness? These look perfect for camping to spread throughout the site, but I don’t know if they’re supposed to be personal use only or if they can be arranged around a perimeter for example.