The three factors that damage herbs in storage are air, light, and heat. If you properly control these three factors, your dried herbs can last just about indefinitely!
Avoiding damage caused by air:
Store the herbs in regular canning jars (Kerr or Mason brand). These are available in the food canning section of your local grocery store, generally in both pint and quart sizes. Gallon sizes can be custom ordered through your store. They use two-piece lids (a flat sealing lid and a screw-on ring that holds the sealing lid down). These jars can be vacuum-sealed using a machine called a Foodsaver. The Foodsaver has an attachment hood that goes over the mason jar (with only the sealing lid in place), and removes all the air from the jar. This eliminates the problems caused by air coming in contact with your herbs. The Foodsaver can also vacuum-pack your herbs in custom-sized plastic bags. The Foodsaver bags come in two widths, and you determine the length of the bag based on the quantity of herb you are sealing. If you make your Foodsaver bag larger than is initially necessary, you can reseal it once you have removed some of the herbs.
If your mason jars are sealed with a Foodsaver, break the vacuum-seal gently on the jar when you want to open it. Use a dime or the end of a table knife (not a pointed steak knife!) and run it around the rim until it becomes tight (between the sealing lid and the glass threads of the jar). Gently pry the sealing lid until you hear the “whoosh” of air rushing into the jar. The lid will then come off easily. If the sealing lid is bent or otherwise damaged during removal, replace it with a new sealing lid before vacuum-sealing the jar again. Boxes of replacement sealing lids are available in the canning section of the grocery store (where you found the canning jars).
The cardinal rule is this: if you open a vacuum-sealed jar containing herbs, you *never* put it away without making sure it has been properly vacuum-sealed again.
If you do not have a Foodsaver machine, pack the mason jars as fully as possible with the herb. Tap the well-filled jar on a thickly folded towel laid on your counter, to settle the herbs and expel as much air as possible, then put on the sealing lid and screw down the ring lid tightly. As you use more of your herbs, transfer the remaining herbs to a smaller mason jar (pint sized), and again remove as much air as possible before sealing the lids. Jars that are not vacuum-sealed need to be kept as full as possible at all times.
I do not recommend using plain plastic bags (sealed with twist-ties) or ziplock bags for long-term storage of herbs. There is a small amount of air exchange with these types of bags. Also, being plastic bags that are not specifically designed for long term food storage, they tend to gas-off into the herbs. For short-term storage only, ziplock bags may be acceptable.
Most of the herbs from Frontier herb come in a metallized-plastic bag. These are three layer bags made by sandwiching a thin layer of aluminum foil between two thicker layers of plastic (**no** aluminum comes in contact with the herbs at any time!). These bags protect the herbs from light and air until they are opened. Though they are not vacuum-sealed, they do prevent air exchange and are a tremendous improvement over the plastic bags with twist-ties that most herb manufacturers use.
Avoiding damage caused by light:
Store your herb jars in a dark place. I personally put them back into the box that the canning jars came in. These boxes have cardboard separators to keep the glass jars from hitting each other and breaking when the boxes are moved. I write the name of the herb in the jar with a permanent marker on the top of the sealing lid. That way, when you open the box, you know exactly which herb is in which jar without having to take the jars out of the box.
As an extra precaution, some people paint the outside of their mason herb jars with black paint to keep out the light. This is an effective measure, but is not really necessary if you put the jars back into the box they came in and close the box well.
Store the box in a dark place such as a closet (preferably one that isn’t opened a lot!).
Avoiding damage caused by heat:
Do not refrigerate your herbs! Yes, it will protect them from heat, but it will also cause condensation within the bag or jar that can cause mold!
Keep the filled, boxed jars in a cool place. If you put the box of herbs in a closet, make sure it goes on the floor and not on the top shelf! (Remember, heat rises.)
The smaller, pint-sized mason jars can be kept in a drawer. If it is a drawer that is seldom opened, just put the jars in with the lids facing out. If you open the drawer frequently, put a dark towel over and around the jars.
When selecting a storage place for your herb jars, make sure you choose a site that will not be subject to freezing.