In the meantime, is there any empirical data on how long the batteries last? It's clear that it depends on use. But maybe someone can give practical examples.
How are you informed that the battery is empty?

How long the battery lasts depends on the use of the live stream / movements. The battery is charged within 2 hours. Yes, the battery can be changed without disassembly. It can also be charged in the camera.
The indoor mount is magnetic, which means the camera can be easily removed. The outdoor mount is screwed on, so the camera could be stolen there too. In general, you have to think about where you mount or camouflage it.