This is how we buy a gallon of milk. 4 (1) quart containers.

Most stores only sell this size.  They cannot be resealed so I use the plastic litre bottle after I open one carton.  The milk I purchased today (Jan 28) is good until April 6 without refrigeration.  The cost for a gallon came to $4.78 at a discount grocery store.  (This is 1% milk.)