I sent my BACTrack in to be calibrated. It was turned around really quick and is working great again! The S80 still performed reliably for 2 years, I finally sent it in once it stopped taking readings (over 200 uses!). I had it back 2 weeks later and I have peace of mind knowing I'm safe to drive when I go out.
I sent this to be re-calibrated because my unit was testing with extremely low values. After I got this back, it still seemed a little low while testing.
I bought this product 4 years ago, it served 44 times. Half of the time the reading was wrong. I finally decided to send it back to get repairs.... just to know it can't be fixed / calibrated and out of warranty.
I have a couple so I can compare the accuracy. They are about a thousandth (.001)of each other. If you see any swing more than that send it in for calibration. Easy to use and fast.