Advice on Audiomoth extended power and case solution

I am leading a project to conduct canopy camera trap and audio monitoring for birds and mammals along a conservation corridor at the Jama-Coaque Reserve in coastal Ecuador. We will use camera traps mounted in the canopy to monitor arboreal mammals, particularly two species of endangered primates and Audiomoth's to monitor bird and mammal use of the corridor. The Audiomoth's will be mounted adjacent to the cameras. These stations will be ~20-40 meters in the canopy. We will be running 20 Audiomoths on a grid to start and hope to expand in the future.

Obviously we need an extended battery life for the Audiomoth's and a good (great) case solution. After reading the literature and all threads about battery life and cases I've come up with my own proposed solution for both building upon collective knowledge of what others are doing. I would appreciate any feedback on our proposed power and case system. 

1. The case will be a IP66 waterproof junction box ($1.40/each) with clear cover measuring 100x68x50 outside dimensions - https://www.aliexpress.com/item/33016702512.html?spm=a2g0o.detail.100006...

2. Acoustic membrane is the MILVENT Adhesive Vents with IP67,IP68 ($0.33/each) - https://www.aliexpress.com/item/32804881418.html?spm=a2g0s.9042311.0.0.7...

3. IP68 Stggo Gore Vent Plug ($6.45/each) - https://www.aliexpress.com/item/32954329806.html?spm=a2g0s.9042311.0.0.7...

4. Tenergy Li-Ion 3.7V 5200mAh Rechargeable Battery w/PCB ($24.99) - https://www.all-battery.com/li-ion1865037v5200mahrechargeablebatterypcbm...

This comes to about $35 per case with rechargeable battery. I plan to solder JST connectors to use between audiomoth and battery so that will add a little more. Will also need to buy about 6 extra batteries to switch out to allow for charging time between maintenance days. Using 4200 mAh (~80%) from the battery recording at 48kHz (our interest is primates, birds, amphibians) for 280 min each day should give us about two months of recording time. We should be able to get about 3 years of life from these batteries. The audiomoth will sit on top of the battery in the case.

I see most people using 3 C-cell non-rechargeable batteries for their systems. I see this being a little less expensive initially (even if using rechargeable C's) but in the long run it will be more expensive. These Li-Ion are also lighter weight as well which I like for transport in the field. We only need about 4-5 weeks of recording time between maintenance so we could go with a lower mAh which would be less expensive. 

Again, I'd appreciate any feedback on our proposed system before we start investing.