I tested before going on my first trip;
My zpap prescription is 10-20, average 15. If your pressure is different factor that.
In my home 70 degrees I can get 16 hours or two nights of run time.
On the mountain around freezing it drops to 8-9 hours. So one per day or bring solar panel - Extra weight or loose a day Tending charging.
I started bring extra toe warmers and slap one or two on the Sherpa each night and put it all with me in the bag and can get about 12 hours. As little as I sleep up high that’s two nights worth. Snd I only turn it on when I’ve begun to dose and not when I get in bag.
As far as back pack hunting only bring Sherpa 50 at 1 lb each and do shorter trips. 1-2 nights = 1 Sherpa, etc. i have 4 total. I will have at the truck a generator or marine battery and the nomad 20.
If I’m doing some base camp/truck camp and have storage resources or closer proximity I’ll use the big battery. A quality AGM battery for trolling motors should easily last a week+. Generators can charge anything I need, as needed.
As far as goal zero, minimum solar panel is nomad 20 which in good, clear summer sun will charge a Sherpa 50 in 4 hours. Double that in actual use in fall/winter mountains with trees and mixed weather. You’ll need to move it to keep it in sun. It does work but weighs 1.5 lbs and awkward packing due to rigidity, but fine left in truck.
It’s all a pain, but it’s kinda the burden of sleep apnea if you warrant it medically, and want to remote hunt. I would not tough it out for a few days especially up high - too great a risk.
Not sure what machine you have, but I hooked my old resmed s8 to a Sherpa think it was done in less than 3 hours. There are 3 or so very small backpack sized machines that you need. They use very little power comparatively, yet as effective as my current s10, just not as quite.
The newest Sherpa I want to say is double the reserve power and only 50% heavier. I’d look at that, especially the connection process. They all need 12v, so cigeratte male female. The old sherpas had that feature plus usb. Most new power packs have only usb. If usb c it’s possible to use usb c, but you’ll have to check with the cpap maker if the make an adapter.