This is a great question about the BW Clip Extreme H2S monitor, and I'm surprised we haven't had it before. A customer from our website asks "How long of a shelf life does the monitor have?" The answer is each monitor has a unique turn-on date that is set one year after the manufacturing date. The warranty is tied to this manufacture date as well. BW provides a warranty for one year of shelf life plus the two years after activation. If you have a monitor that is past its turn-on date, you can still turn it on and use the monitor. As long as it starts up and displays normally, it's functioning properly. And depending on when you turned the monitor on, you may still be operating under warranty at least for part of the time. For example, if you turn the monitor on six months after the turn-on date, the monitor will still be under warranty for the remaining 18 months. Does that make sense? Hope so. The next question that logically follows is regarding the safety of the monitor after the factory warranty expires. The answer is that as long as the monitor still has the countdown on the screen, it is operating properly. The experts say there may be some battery drain if the monitor isn't turned on within the proper time frame, and could conceivably stop working before it has run for its entire 24 months. But unless it's turned on years after the listed expiration, that is unlikely. Clearly the safest option is to use your BW Clip Extreme within the listed time frame. If you have follow-up questions, or variations on this theme, please don't hesitate to comment on this blog, or give us a call at 1-800-829-9580.