How long to keep potable water in holding tank

My fresh water tank hasn't killed me yet. I sanatize, drain and refill once in the spring and it hasn't been drained since. Likely mid October will be the time to drain and winterize.

Same for my hot water heater.

Your milage and comfort level with water storage is probably different than mine. There's a vocal group on these forum that are quite afraid of their onboard water system, and tap water in general.