It is important to remember that Kodak is no longer acting as its own distributor for many of their products. It may be that there is a distributor out there who came upon a bunch of material with this expiry date.
I believe Agfa stored their uncut rolls at -10C. For shorter storage any refrigerator set to a temperature for proper food storage 0C to 4C should be OK.
For Food refrigerator are nominally at 4C while home freezers tend to be set at -18. So -26 would likely be the limit of what a home freezer could achieve should you want to emulate AGFA's Practice..
Its been awhile since I read an article on Agfa. I do remember a temperature of -10C being given. A temperature of -26C seems rather low to maintain and still watch the bottom line. The lower one goes below 0C the more electricity that is needed and the relationship is not a linear one. Below freezing cosmic rays and background radiation become a greater problem.
Just for clarification. I think you are saying that cosmic rays and background radiation become a greater problem in comparative terms and effectively outweigh any improvement in a lower deterioration rate that below freezing temperature can produce. So the improvement in lowering deterioration at -26 compared to -18 is minimal and the main causes of deterioration are cosmic rays and background radiation.
You are not saying that below freezing actually increases the effect of cosmic rays and background radiation? Thanks