Hi,
Everything can be stored in the refrigerator but since all items are perishable food items and contain no preservatives, it is best to brew as soon as possible to ensure freshness. We recommend that customers only buy enough supplies needed for one month of brewing so that nothing sits around long enough to go bad. Just like with cooking, the fresher the ingredients, the better your final product will be.
Different items in the kit will go bad at different times.
Grain: Milled grain has a shelf life of about two weeks before starting to go stale but you can keep it fresh longer (up to 3-4 weeks) by storing it in the refrigerator. Unmilled grain can keep for a year or two if store properly (not too warm, humid).
Extract: Liquid Extract will last about 1 month before mold will start growing on it. You can scoop the mold off and kill whatever remains during the boil, but you can also add a thin layer of neutral vodka over the top of the extract and it will keep stuff from growing on the surface. Dried malt extracts can be stored for a long time because it has moisture removed from it making it harder for things to grow on it.
Yeast: Liquid yeast has a shelf life of about 6 months but can still be used after that point if a yeast starter is made. If any new yeast grows in the yeast starter, then it's ok to use this yeast to make a batch of beer. Dried Yeast packets normally have a shelf life of a few years. You should store yeast in the refrigerator but avoid lowering or raising the temperature of yeast too fast. Large temperature swings cause damage to yeast cell walls.
Hops: Hops can be saved for up to a year in the freezer, but after 6 months the bitterness will start to break down and will weaken with time.
Hope this helps,
Aaron Smith
Austin Homebrew Supply
