We boondock and dry camp in a class A a lot. All of our favorite campgrounds are in national parks and we don't often have electric hook ups.
We have added 600W of solar and so never run out of electricity. But, with on board generators, running out of electricity is never a problem with a class A - running out of water is.
Knowing we have limited water and black/gray storage, we conserve. In warm weather, if starting with full fresh and empty black/gray, we can go 7 days on 85G. One of the benefits of many (not all) class As is they can carry a lot of fresh water.
So, if we got a tote for fresh water and another for black and gray, we could conceivably go for months at a dry camp location, even without solar. Our limit would then be our gas tank (80G) and how long and often we ran the generator.
Currently, we typically boondock/dry camp for 5-6 days, then go dump and replenish water and then find another place to camp.