Product review (5 stars): Maybe battery choice matters?
I've had my set for about a year and a half.  It works great.  I live within 4 miles from Central California's Pacific Coast, with a moderate range of temps and a wide range of humidity, including occasional fogs and occasional hot, ultra-dry winds in summer and fall.  I have a considerable experience with alkaline batteries in cold temperature of the Sierra so I was careful to use a lithium battery in the outside sensor.  Lithium batteries perform more reliably in cold, even subfreezing temperatures.  Maybe that decision played a role in my lack of sensor problems.  The only gotcha to mention is not about this unit, but about the battery alternatives.  Alkaline batteries are gradual in their decline; as they decline their performance can affect the fidelity of the sensor readings and such affects on accuracy may last a week or longer.  Lithium batteries, while more expensive and maybe harder to find, not only last a bit longer, especially in freezing temps, but their drop-off in performance is comparatively sudden, shortening the period of reading inaccuracy to only a day or two.  The indoor unit's signal strength indicator is the telltale for waning outside batteries.  My initial lithium batteries in the outside sensor lasted almost 15 months.  My experience with these devices has been wholly satisfactory.