Thank you to the moderators for following up on my request!
Just a quick update to tell you about our Power of Standby experiment, which we documented on
https://www.theredreactor.com/2022/03/05/the-power-of-standby/
We had a Pi Zero powered by the Red Reactor using 2x 3000mAh batteries, set up with an RTC alarm to boot up every 4 hours to take a moisture sensor reading, email it out and turn itself completely off again. With these measurements we could show the benefit of the Red Reactor's ultra-low standby current (few uA) for sensor applications, and our setup was able to take 481 separate readings (it took 6 readings per day) before finally signing off from duty today.
So, if you just needed 1 reading per day, we've shown that it could run for well over 1 year on batteries. It’s funny, I kinda got to like seeing emails from my Pi every day…