Our recent run down to Seward AK (weather was awesome) for 2 nights, resulting in 2 people taking 2 showers each, coffee making, the normal bathroom usage prepping stuff (DW ;) etc. Kitchen use was minimal as we treated ourselves to the best white king salmon lunch ever!
Of course, as usual, we ran our of water, even with light use. So for us, two days, two night max expectancy of water for boonedocking.
Got home yesterday, found the winterization tap, cleaned it, checked it and am now prepared to add water in the main tank for future use!!!! YEAH!!
I have never winterized with antifreeze (RV); I don't do it this way. I simply open all faucets and outlets, flush the entire system, blow air through lines and leave the lines open. I pour a little RV antifreeze into the holding tanks (after they are cleaned and flushed of course), and leave things till I'm ready to go. Makes my life so much easier, and if I ever get a wild hair in the winter and decide a winter campng run is needed, I just grab the Navie and go.
So, the winterization tap is now my added water tap!