I have the same experience as the others who gave commented here. You need not worry about the contact sensors falling off. They stick well to the surfaces.And if for some reason you must remove them, you can reattach using super glue. I did that for a few which were initially put leaving more than the recommended distance apart.

You do not need to worry about the products falling if you heed to the laid down procedure. It is very solid on all recommended surfaces and even tough to tear it down physically to my experience. At the same time, do not forget that, nothing is permanent.

I have been using the sensors for more than a year and have no such problems. The sensors hold up well.