Shelf life of water stored in collapsible PE containers

I represent an emergency services organization in Washington State, USA. We are considering buying collapsible PE containers specifically designed for water storage. Does anyone have scientific, empirical, or just 'gut feel' data on shelf life if stored in cool, dark, dry places?

PE is a thermoplastic polymer. It means the molecular structure is loose with big gaps and cavities, a.k.a. highly permeable. It's ok for short-time containing liquids, like a couple weeks.

For a longer shelf-life, you need to use thermosetting (more dense microstructure) or composite materials.

I should have been more specific about shelf life. We plan to purchase and store bags in original containers. we're trying to get an idea of how long we could store them, unused. Thanks.

Aghhh. I misunderstood your enquiry. You meant the shelf-life of the PE bags, not to-be-filled water.

The common warranty time of PE is about 1 or 2 years, before the visible degradations (e.g. chalking by diffusion of additives, yellowish tint)

PE is a hydrophobic polymer and quite inert so that the humidity has not got big impact in storing condition. Avoiding some extreme situations is good enough, like wetting, heating up to 100°C, near strong organic chemicals (e.g. MEK, toluene).