I mostly dry camp around 9-10 days in a row.
Black tank is my limiting factor.
You can always pack a few 5 gallon jugs of fresh water.
Grey water, we wash our hands using the outside shower (sometimes dishes or corn on the cob water) all goes into the 5 gallon home depot bucket for putting out the campfire every night.
The power stuff I went double double.
Built in Onan 2500LP, Honda EU2200i, 360 watts solar, 3 AGM grp 31 batteries (300 AH total), 2000 watt PSW inverter, 100 watt home made suitcase solar backup.
Batteries have a shunt with in and out meters.