Well.

1. I would power A0 (ADC)through a digital pin. This way it reads voltage only when needed, not always connected to battery and draining power.
2. Besides powering the nrf radio through a pin (transistor) is a good idea as well.
3. Putting the mcu To sleep sure will add few more days to the life of the battery.
   Battery in correct connections should live more than couple of years, I had ultrasonic distance reader project connected with nrf and pro mini. That lived months without a noticed drop in battery

Hello,
im kind of lost, i need to install a distance sensor buried in a well of water, and will need a lot of tweaking and reprogramming until i get the desired correct measurements.
so i need OTA, extremely low power (battery powered, sleeps most of time), so i went to ultrasonic sensor HC04 which is even powered through GPIO of pro mini, and an nrf24l01+. the main problem is OTA. My concerns are:

1. should i burn MYSBOOTLOADER on sensor and Serial GW ?
2. if bootlader burnt, any sketch can do the OTA?
3. should I use only MySensors GW SW, or can i have my own sketch.
   Any ideas are welcome.
   Thanks a lot

hello,
i know it is late, but others could see it too.
i had the same problem running small (LOW POWER) modules on power banks, because the battery or power bank has a built in power meter, while it is charging and consuming power, there will be power on the USB port, but the arduino's consumption is very tiny regarding charging a phone. you need to disable this feature somehow.