How many days to fill gray and black holding tanks???

My family of 5 managed 7 nights on our 35 gallon fresh (plus 6 for water heater?) and 35 gallon grey tanks. It took a couple years to change our habits to accomplish that. We use house water for teeth brushing, washing hands, and washing dishes. We use campground showers and bathrooms except for middle of the night emergencies. Our first trip we only lasted 2 days. It sucked packing up to take TT to dump station just to repark and set up.