There should be a date on it (there have been on mine at least). As long as you seal it back up and stick it in the freezer it should keep until at least the date and may still be good for a while after even (I am guessing it loses some of its nutritional value eventually). I do think the freezer will help keep it fresher but I have no proof LOL.
When I contacted a seller of CC I specifically asked this question. There's a expiration date on the CC itself, and as long as it's kept in the freezer it dramatically extends its shelf life.