Just thought I’d chime in that I bought a 2-pack of plastic reflectors that came with adhesive pads (at a local farm/tractor supply store). I’m hopeful that this mitigates the moisture issue I was also experiencing - really warm day that got cold at night triggered lots of false alerts. Thin layer of moisture would form on the stickers I got with my Garadget.
I didn’t want to mess with chunks of foam and double sided tape, so I decided to try these. The reflection rate was the exact same reading as the stickers, so the next/final test is a warm day with a cold night. 
Attaching three pictures: reflector mounted on top of my existing stickers, Garadget laser hitting reflector, and the original packaging.