I do fresh water tank once a year, I would say no requirement for every trip. I also drain tank and hot water tank prior to heading home after a trip, leaving water in, can allow nasties to develop.
Like yourselves, water from tank used for washing/shower and, cooking, as most of the times water will be above or at boiling point. we take along drinking water for us an our dog, in a separate container.
No questions are silly or laughable, always better to ask..........cheers.