I've had two 2016 headbands that stopped working, one of which I had been using for only two months. I sent the second one back to Interaxon's office in Toronto so that they could look at it, and here is their response:
To provide an update: my colleague Marta in our hardware department has finished testing your returned unit. She found that the sudden problem was being caused by the frequency with which the flex (the sensor strip at the front of the headband) was being cleaned. She attached a new flex, which fixed the issue.
As a result, I would emphasize trying not to clean your replacement headband too often or too vigorously. A gentle wipe with alcohol once every 10 sessions or so should be perfectly sufficient.
I had been cleaning the headbands with alcohol wipes after every session. In both cases, though, the failures didn't appear to be gradual – they just suddenly stopped working.
how many uses can we get out of one headset
FWIW, they sent me a replacement headband five months ago, and I've been using it every day without any problems.