Storage of Fresh Water - How Long

Last time the 30 gallon fresh tank on the truck camper was filled was in TN in Oct 2021. The water was treated city water. Unless taking a trip, the truck camper only gets taken to town (dog park and shopping so the dog goes with us). We carry a 3 gallon jug that we refill in town at one of the water filtration stations for our drinking/cooking water. Since I have been working on the camper (including some plumbing work) over the past winter and summer, I've had the cover for the fresh tank off. Water has no green or black things in it. Nor does it smell stale or "off". Works very well for flushing and washing hands. At some point it's going to need to be filled again as it's down to 1/4 of the tank (according to the tank level gauge). I think it will be taken it to town and filled from the city water spigot at the store my daughter works at.