Once you have crafted your homemade room spray there are few useful things you can do to help it last as long as possible. Generally, most blends will last for a couple of months, so if you are not intending to use it regularly, it is perhaps better to create the mixture in a smaller bottle. Then try the following when you are ready: Sterilise the bottle using boiling water or isopropyl alcohol before making the spray. If you are combining multiple essential oils, combine a blend of top, middle and base notes as this will help the scent to linger for longer. When not in use, store the bottle in a cool, dark place away from direct sunlight and indoor heat sources. Also check the dates on the essential oils before you use them, as using nearly expired – or expired – essential oils may cause irritation and other allergic reactions.