Although work on the controller PCBs have stalled, I have been fortunate enough to use the exact hardware in 2 other projects: 

1. A remote logger for an oceanographic instrument in Greenland: measure, transmit data, sleep

2. An long term underwater scanning sonar: do a sonar scan of the seafloor, sleep. 

The second has been my avenue to produce my first paper and submission to the HardwareX journal, a small bucket list checkbox to tick. Instead of a photo timelapse I was able to generate a timelapse of seafloor changes for 30m over 3 months. 

I have been eager to continue with this project again, with a new, improved controller PCB, but as years have passed since I have started the project I decided to check the market. And damn. I found a product that makes my efforts near unnecessary:

The Witty Pi 4 (L3V7)

https://www.uugear.com/product/witty-pi-4-l3v7/

Finding this thing made me swear a lot. I immediately bought one to check out and damn, it really is a near drop in replacement for my controller. UUGear has created an extremely capable companion board for a pi Zero, with some really useful and sensible software too. 

If anyone ever in the future looks at this project and wants to build something similar, look no further for handling your Pi sleep cycle. Forget all the ploys I have mentioned before- even the TPL5111.

There are of course minor compromises, but really, everything you need to make a sleeping pi is here. My board of choice, the Witty Pi 4 L3V7 comes at a cost of about 24 EUR.