One of the home improvements you can do to your house is to add Water diverter to any pvc running from ac units. This diverter takes water away from the treated zone and allows the termiticide to stay where it is put. One of the keys to termite work is putting the termiticide to the place where the termites will go through it. If water is constatly running through it, it will over time diminish the effectiveness.
This device isn’t in the best of places, but is able to divert some water away. The sidewalk somewhat blocks the pipe from extending far enough away. But this device can help and does.
So here is my theory on longevity of termiticides in Arizona. Under concrete I believe Termidor can last up to 15 years and if it is on the outside of home I cut that rate in half to 5 -7 years. Now anything can cause this to break sooner, something under the slab such as rocks, paper or anything left over from construction.