How long does a wall clock battery last

The battery of my wall clock died yesterday. This clock has been in my room for quite some time so I wondered how much is typical power consumption of a wall clock. Since I have different clocks at home which operate differently (continues and single-tick-per second mode) I thought i should see how does their driver differ from each other.
When started to measure the power, i realized that we must be very careful to properly measure the current rms, since a multimeter in many cases can not properly measure rms value of low frequency signals. I used my scope to measure the current waveform and it turns out that my single-tick-per second mode clock may run for 1000 days while the continues mode clock may last approximately 300 days. The video became very long and i decided to open the driver in a separate video and compare the two later.