If kept in a cool dark place, they’ll be pretty stable, but you’ll still want to churn your supply by using one and filling it then put it at the “back of the line”. Use a container or more per day for cooking and cleaning and you’ll rotate through your stock according to however many containers you’ve got in that number of days.

Glass is probably the safest long-term container, sadly. I know it's heavy and fragile, but even stainless steel can develop algae over time; you're certainly welcome to try both and see what happens.

I tasted a water that was in a plastic container standing in my kitchen for 2 years and i found 2 years was way too much in my case, the taste was heavy plastic. The container was sold as water container. If i were dying from thirst in the middle of the desert, i would probably still drink it, otherwise hell no, it was disgusting.