What a stupid design by Nest. If they know that battery will fail they should at least make it user accessible when removed from mount. Replaced mine. It’s a pain getting to the battery and it’s easy to crack the faceplate when prying it off. Also the plastic tools included with kit will fail before you’re into the device.

If you can manage to get to the battery without destroying the Nest Doorbell it’s worth it to get a few more years of use.