It has been holding so far. Measured all levels and all rooms. Used for over a year in all seasons (Rn levels vary dramatically!) to get readings until decided to install radon exhaust finally. Reset this detector after the radon fan addition to take new readings which took usual two days. Also, installer provided a mail-in kit for the final reading. Sent that one after three days of being opened. Got mail-in results and they were exactly what this detector was showing. So, it is still working great!
Got about 5 of these and all read 1.3 to 1.4. when tested with a professional one I got the same. Plugged in is great since no batteries to remove. Have them on the floor all over the basement. When I placed one in my neighbor's house the alarm when off with a final reading of 12. That was the same reading they got from a professional.