At the grocery store, most raisins are sold in boxes or packages you cannot see through so it is difficult to judge its freshness by just looking at the packaging. However, most packets can be squeezed so you can get some idea of how fresh the product is. So, choose the product that submits to the pressure.
Proper storage is important for raisins. You can seal raisins in an airtight container or bag and store in a cool, dark place. Most kitchen cabinets are too warm. A month on the shelf is maximum, after which they begin to dry out, darken, and lose vitamins.
Refrigeration is recommended for storage longer than a month. Under refrigeration in a properly sealed container, raisins can last six months to one year.
As they age, be sure to examine them carefully for insect infestation before using.