2 cents worth, and not sure it is worth that:
We don't trust the tanks on these rigs, they have a bad habit of splitting and breaking and flowing stuff out the bottom.
We travel with as little water as possible.
We have gone 8 days without unhooking the rig and the truck, BUT, every other night we hookup up water and sewer in a real campsite with as much power as we can find and clean everything and take really LONG showers.
Yes, we have boondocked at Quartzsite, 15 nights, in 9 nights, I used 40 gallons of water (don't ask about my electrical use tho, gulping). And, yes, we took showers, short, don't let the water run showers, but, showers, two of us. Dishes too.
Two words: WET ONES! aka, baby wipes. They are your best friend. You can wipe dishes clean with them and then wash when you have full hookups. you can use them on baby bottoms, fur kids, and momma and daddy too. They are great for quick cleanups of just about everything you can think of. And, save oodles of water.
Yea, I know, more than 2 cents worth and still not worth it!