Here are a few tips on how to store and extend the shelf life of essential oils and other aromatic ingredients, such as absolutes, CO2 extracts, and oleoresins.
To prevent light degradation, store your essential oils and other aromatics in colored glass. If your essential oils were packaged in clear glass, either transfer them to colored glass bottles or cover the bottles in dark paper. Other people prefer storing them in lined aluminum bottles.
I do not recommend storing undiluted essential oils, absolutes, CO2 extracts, and oleoresins, with glass droppers. The glass droppers have a rubber bulb, and over time many aromatics can degrade the rubber and ruin the aromatic. Storing your products made with essential oils (or absolutes etc) in bottles with a rubber bulb is perfectly fine (since in products, the essential oils are well diluted so won’t break down the rubber).
Store your essential oils and other aromatics in a dark, cool, but not damp place. A few good suggestions are in a refrigerator, a cool but non-humid basement, or a wine cellar. If you can’t store them in any of these places, then I recommend storing them in a box or a cupboard in the coolest room in your house. I do not recommend storing essential oils in the bathroom, because the humidity and constantly fluctuating temperatures can greatly reduce their shelf life.
As you use up your essential oils, absolutes, CO2 extracts, and oleoresins, it is always a good idea to repackage them into smaller containers, since this reduces air space and helps prevents oxidation. Keep a small supply of colored glass bottles and vials in a variety of sizes for this purpose.
Label your aromatics well with the date of purchase. This way you will know how old they are, and which ones need to be used up more quickly than others.
You can use older essential oils (ones that are nearing the end of their shelf life but are still good) in cleaning products, in potpourri, and to scent clothes, paper, sachets, etc. If they are way past their shelf life, and are not one of the essential oils that ages well, I would compost them outside.