With the limited cooled space in our vehicle items like milk can take lots of space. For a 10 day adventure a full gallon of milk is a good figure. This takes a big hole out of the cooler. Anther option is powdered milk, yuck.
I have started using aseptic packed milk. I order Parmalat Low fat 2% Long-Life Milk on the Internet. The milk is in 32 oz. containers that have a shelf life of 6 months or more. During our travels we only need to use space for 1 32 oz. container in the cooler. The rectangular boxes fit well in our ARB fridge.
Parmalat is also a great part of at home emergency preparedness.