How long can you keep water in the tank?

[SlowrideHD]

I generally don't drain my fresh water tank unless the source water at my last campsite was stinky or discolored. I don't have to fully winterize because of the fairly mild winter season at my home (I leave the heat set to 40 F). I did flush out my water heater tank for the first time last fall when I checked the anode condition and was surprised at how much of the gritty aluminum/zinc remnants were in there.
I drain my tanks fully at the end of the season and last week when I (de-winterized) and filled the fresh water tank, I added a 1/4 cup of bleach. Then used the pump to run this mix through all the lines and fixtures. I'll let this sit in there until we get ready to go on our first trip of this season (which may be a while due to the current crisis).
I occasionally use a bit of the camco water fresh additive if we are at the gulf in very warm temperatures and always have one of the blue filters on the camp fresh water supply. We also have the kw-1 filter in place and a Berkey travel system but have used a Brita pitcher before getting the Berkey. We often make coffee right out of the tap if the water smells fresh.
Have been following this process for decades without ill effects. My grandkids and I also drink from a spring that bubbles out of the ground on their mountain property when it is flowing freely.