Fresh Water Tank--do you empty it?

I sometimes camp where there are hookups for water, and sometimes not.

When I do fill it I never end up using nearly all the water.

I wonder whether I should empty it after this or just leave the water in there until the next time I camp.

Pros and cons to both I guess. No point in hauling around extra weight, but also no point in wasting the water and having to take the time to fill it again next time.

I don't really drink the water out of my tank. I pretty much just use it for washing dishes and showering.

It is also extremely slow to empty (unless there is a bigger drain than what I am using which is like a lower water drain). I had about half a tank today after camping and let it drain as I was driving. It took about an hour. Made me wonder if perhaps the intent was not to empty it but just to keep water in there and top it off when needed. I guess water doesn't really go bad. Not sure if mold or mildew is more likely to form in an empty but still wet tank or a full tank.

Last thought on this is about weight distribution. It did occur to me that swapping back and forth between empty and full would change the weight distribution in my trailer and maybe affect the way my WDH should be set up, in which case perhaps it is better to either set it up with or without water and then drive that way all the time.

What do you do????

thanks
Matt