Thanks for the input. It's probably simplest to agree I carry too much water. I'll probably continue to do that for awhile until I learn what we actually use. Generally we arrive at a water source with about pint and a half apiece. We don't always start with a full gallon. That's just the max.
WARNING: Graphic discussion of body functions. All of us are different but I keep my water consumption between 3 and 6 quarts per day. I get constipated if I drink less than 3 quarts per day - a moist colon is a happy colon. If I drink more than 6 quarts per day the result is that I flush out nutrients and minerals and risk osmotic diarrhea. My colon just does not have the capacity to absorb more than 6 quarts per day and that is hiking in triple digit weather. If I am drinking more than 5 quarts per day I need extra potassium so that my body can absorb the water.
Sun protection is important. Not sunscreen, but long sleeve shirts and full brim hats or even an umbrella.
If I allow my heart rate to go too high for very long then I "burn out", and can only hike a few hours per day. If I hike slow and steady then I can hike a lot of hours a day. Interval training is very good training, but is not a good hiking pace.
It is a good idea to push your aerobic capacity when you train, but not on a multi-day hike.