Most of our camping is done without any hookups unless we're on a trip to the Oregon coast or something similar, which isn't really camping but more just using the trailer as a hotel. On camping trips we practice conservation and bring along some extra to supplement as needed and haven't ever had trouble making it several nights. I do have a couple of 5 gallon potable water jugs I always pack along - they just look like gas cans only blue. I generally toss them into the tub to keep them contained.
A couple of batteries are a must, and LED bulbs are a good investment. I also cheat and generally pack along a generator.
Edit - I not a fan of the collapsible jug linked above. Had too many of them spring leaks on me. I prefer something like
this.