Datrex doesn't list storage temperature ratings but Mainstay does.

From the Survivor Industries web site the Mainstay food storage temperature range is -40F to +300F and for water packets it's -40F to +210F. The shelf life for both is five years.

That fits the bill. Datrex is also rated at five years though they don't list the storage temperatures.

Thermal cycling, or repeated freezing & thawing, is pretty tough on most materials when water is involved and can lead to microfractures, or empty water containers when you need them most.

Water can: the water packets are going to have a much longer shelf life than anything I can do at home with a water can. Also, small water packets are easier to put in several places around the car than a big water can (one water can in the car would be like all-eggs-one-basket but I'll put several water packets in many different places in the car).

I definitely hope to never eat that stuff except for the test run! The food I only plan to eat when the alternative of not eating it is even worse...