Storing bakes like this in a large glass jar with a clip-top lid (like a (paid link) Kilner jar) helps to keep them exceedingly fresh. When stored this way, these oat and date slices will stay fresh for up to 5 days. If you do not have such a jar, it is worth wrapping the bars in foil before storing in an alternative airtight container. These sticky date bars can also be frozen for up to 2 months. Just let them thaw for several hours on the countertop when required.