Sonoff sensors do not go unavailable in ZHA when no battery

I’ve googled this lots and haven’t found a consistent story so hope somebody can help.

I’ve installed Home Assistant on a Raspberry Pi4 with a Raspbee II card. I’m running ZHA with the zippy-deconz library. I have two Sonoff temperature sensors. I want to be alerted if either of them goes offline. I’ve tested this by removing the battery from one of them to see what happens. All that happens is that the sensor sticks at the temperature when the battery was removed but there’s no status update.

Is there any way of getting the sensor’s status?

As a workaround I raise an alert if the temperature hasn’t changed for 4 hours!

Well, not for the first time I seem to have come to a conclusion too early! [Ed. surely not?! :o)]

It seems that if I wait six hours, the thermometer does become unavailable. If I put the batteries back in, then the temperature is soon recorded again. I’ve tested this behaviour twice now so I’m confident in it. Six hours is fine for my purposes. I imagine there’s a way to change this but I’m happy with the default.

Sorry to anyone misled by my question and especially to the developers.

in my case i have two osram lights. but unfortunately some hours is unacceptable for me. because I have automation which involves whether the light is available or not. with deconz, it takes 1 minute to change the status from off/on to unavailable.
still if someone knows the solution to update the change quickly please let me know here.