The Funky v2 loaded with my low power test code that I described here has stopped sending transmissions yesterday. The Funky v2 was powered by a fresh CR2032 battery with 220mAh capacity. I use an integer counter that overflowed few days ago and started counting over again. The total number of transmissions reached 73062; These are sent 20 seconds apart so that the test can happen in a reasonable amount of time. I suppose the code could have been optimized further, as @Dimitrios noted in the comments of the original post, I could reduce transmission power and will probably achieve much better results. So since the transmission of data is the most power-consuming task, this number of transmissions gives me a pretty good idea on the estimated run-time. If I have 73062 transmissions per battery and do some ADC measurement and sending every 2 minutes, that would mean roughly 100 days of run time on a CR2032. Running on couple AA batteries will give me years of run time; I am pretty happy with the result.