As long as my "FULL" level still works, I don't really care what the "1/2" or "1/4" levels say when I know I just emptied the tank.
Besides, I carry a full fresh water tank all the time (30 gal) and use it first, even if I'm at a full hookup site... My gray and black tanks are 30 gal EACH, so I pretty much know I'm not going to fill either tank with my full water tank.. :)
I only go on 4 day weekend camping trips, so 30 gal is more than enough for 2 of us.. No showers, as our shower is a "closet" now... :) If I need to take a shower, I'll pay a buck fifty and use the State Parks facilities.. :) If they don't have a shower, I'll take a nice sponge bath and be just fine...
I love taking long, hot showers... Who doesn't?? But, when I'm "camping", that's not something I really care about doing.... Heck, I'm "CAMPING", right?? ;)
Each to their own...
Mitch