Have you considered preserving the lemons instead of only the juice? Here is a recipe I love for Moroccan Preserved Lemons that can be used for all kinds of dishes:

5 lemons, quatered but still attached at one end (don't cut all the way through)

1/4 cup kosher salt

juice of about 8 additional lemons

Rub bit of salt inside each of quatered lemons. Pack tightly inside 1-quart glass jar. Add remaining salt and enough lemon juice to completely cover. Seal the jar. Let stand 14 days at room temperature, inverting the jar every day. Before using, rinse each lemon in water. Store covered in fridge. Will keep indefinitely.

Source: The Frugal Gourmet on Our Immigrant Ancestors