Another way to save space is to simmer it until it is reduced by one-half...
...(or more), then freeze. When you want to use it in a recipe, you can add water and boil to re-constitute to regular strength.
The concentrated flavor of demi glace is another option. Reduce by simmering until the stock is the consistency of syrup. This is not as easy as it sounds. It requires diligent heat control and a careful eye towards the end so the syrup doesn't scorch.