As stated it's your rig and therefore, your rules. For me, I travel with supplies to last at least two full days of heavy usage. There are always things that can go wrong and you could be stranded in a remote spot for say two or three days and need water etc. For that type of contingency I'm prepared, if were going out by Muley Point in Utah, I'll fill the water tank and drain the grey and black tanks at the last full hookup campground before going.
Like my Boy Scout grandson says, Be Prepared.