Handbags   (The sad, the bad and the ugly. Non-productive stuff here.)

Well, yes tonker BUT the transmitter draws current when the bell push is activated, and the receiver draws current ALL THE TIME, as it is in standby mode awaiting to detect a signal from the transmitter.

So the transmitter batteries last about seven years.
The receiver batteries last about eighteen months.

A change to cold weather tends to prompt a failure of the former batteries, so it would not have been unexpected a few days ago, though test revealed it to be the receiver's batteries expired once again.