We own about 8 plastic containers for bagged milk. At any given time, several of these are down in the cellar freezer with milk bags already placed in them. As the milk in the fridge is used...a new container with bag is retrieved and thawed. It's not a problem and we've just done it for a long time now. Makes sense to me...but then no one asked.
As for the metric system...we were both already out of high school when it was imposed upon us. Some of my life I do in Metric...and some in non-Metric. Oh well...