I agree with most of what you say, except -Goofproof wrote:... Now Days batteries are low maintenance and require very little water topping off, or none, so basically tap water makes little difference, like changing the air in your tires in the winter.
I use a 480 Amp-hour bank of deep cycle batteries on the boat, doing charge/discharge cycles daily. They last 6-8 years; If I treat them real nice they might go 10. I have to add water several times a year, so its worth it to keep a jug of distilled in a locker. "Maintenance Free" batteries simply add a bit extra so the they will die in a programmed amount of typical automotive use. Proper deep cycles still need watering if cycled frequently.
I generally say its silly to use distilled in a cpap if you can drink the tap water, but in Paris I found the tap water so foul I got bottled water. Also, I usually use hot water, but in Iceland the hot water tap is often sulfur water from hot springs, while the cold is glacial melt.