I used to work for Drager SA and our company policy at the time was that the O2 cells supplied to the customer must have at least 6 months shelf life left(the guarantee date is shown on the lid). If the cell failed within the guarantee period we'd replace it free of charge.
I know that in Netherlands they kept track of the O2 cell's serial nr and if it fails they will also replace it but you'd pay on a pro-rata basis. Sort of pay-as-you-go type of thing.....
