@jwei
We have at least 2 power "incidents" a month. Sometimes it’s just long enough to reset the power on the microwave and oven. Othertimes I come back and my surge protectors have turned off and have registered an "Extreme Voltage Shutdown" situation were either a brown out or white out has occurred.
In terms of long term battery needs, about 1 time every three months. This is at least the third time this year, and once was due to a storm, and once... was some other random thing.
The complete lack of predictability is why I keep everything on a surge protector, whether that ruins the imaging or tactile feeling of the music or not. (it does not).