Generally speaking, a bag of potting soil is good for about six to 12 months if it’s stored in the right temperature and environment. Unlike plants that may not enjoy cooler temperatures, potting soil remains freshest when it’s put inside a cool, dry place. However, this only applies to bags of soil that have been unopened. If you’ve previously opened your bag of soil and are looking to store leftovers, make sure to put it in an airtight container. Think of storing soil the same way you would your canned goods. Unopened canned goods in your cabinet can usually last for up to a year. However, as soon as they’re opened, they’ll spoil if you put them back in the same environment. Your plant’s food is the same way.