Technically shochu does not have a shelf life since distilled alcoholic beverages are not so high in sugar and/or protein content. Shochu is usually more than 25% in alcohol content, so technically it can be enjoyed for a long time without risk of decomposition. Many times people age shochu more, just as whiskey enthusiasts prefer well-aged bottles.
Shochu should be kept in a cool, dark place. Once it is opened, the taste of the shochu begins to change progressively as time passes.