Hmmmm, we had two cheap quartz wristwatches with a drift of +/- 15 seconds per month, and they were allowed to run for 5 years, drifting in opposite directions, we might expect a difference between them of 0.5 hours.
So having two of these detectors going wonky with "just" a 4-hour difference doesn't seem too far outside the capabilities of some kind of "replace me" timer circuit.
Obviously it could also be Invisible Evil Gas Traces, and the impact of being wrong is severe, so I wouldn't blithely dismiss the alarms as planned obsolescence either.
> Obviously it could also be Invisible Evil Gas Traces, and the impact of being wrong is severe, so I wouldn't blithely dismiss the alarms as planned obsolescence either.
And that is why I only buy CO alarms which display the ppm they measure.
"I'm out of sensor lifetime / battery, please replace me" is a very different level of priority than 300ppm CO. And how I react to 300ppm is very different from how I would react to 3200ppm.
So having two of these detectors going wonky with "just" a 4-hour difference doesn't seem too far outside the capabilities of some kind of "replace me" timer circuit.
Obviously it could also be Invisible Evil Gas Traces, and the impact of being wrong is severe, so I wouldn't blithely dismiss the alarms as planned obsolescence either.