You've gone out and bought a candle, put it in a drawer and forgotten about it. Years later you take it out and wonder if you can light it - can candles expire? Most organic things expire and only have a certain shelf life. Whilst candles do degrade with time there are five things to consider: type of wax, fragrance power, light, decorative elements and storage conditions.
Type of Wax
Parafin wax can generally last indefinitely, all other things equal.
Soy wax is easily good for one year but can last for 2 years if stored correctly. We don't add any preservatives so it's organic.
Beeswax was used as a preservative in Ancient Egypt, where it was used in the mummification of Pharaohs. It was also used to seal the coffins to make them airtight, to further preserve the mummies. So needless to say, beeswax can last for a very long time.
Fragrance Power
Sometimes it not so much a question of asking can candles expire, but whether it still has its full scent. Over time scents erode, particularly if candles are not kept sealed. So you might find after a couple of years that the scent smells a lot less. Still nice, just less of it.
Light
This might take you back to your school science classes. Excessive exposure to sunlight (UV light) will result in the colour of a dyed candle fading.
Decorative Elements
We decorate our candles with several things such as crystals, flower petals, fairy dust and for our skull candles, grapefruit peel. The crystals, flower petals and fairy dust obviously don't have any expiry considerations. However, we don't dry our grapefruit peels, as we like them to look fresh, so just keep an eye on skull candles if you keep them for a long time.
Storage Conditions
Storage conditions are important. Generally you want to store your candles in a dry cool environment, sealed if possible.
Unsealed candles in warm moist environments can lead to mould developing on the wax and if this happens, it has expired. Do not attempt to light or clean the candle, or mould could go into the air, sadly you will need to throw the candle away, it has expired.
It should be said though that the purpose of a candle is to be lit and smelled, to experience - whether that is for the purpose of relaxation, mood ambience, aromatherapy, etc. So it if have a candle at home, why wait to experience it? If you happened to watch The Big Bang Theory, you'll remember a funny scene where Sheldon does not want to play with his Spock toy, but wants to keep it in its box. In the end, Spock appears in his dream and reasons that the purpose of a toy is to be played with, so to not play with it would be illogical. By the same token, a candle is meant to be burnt, so to keep it away unused - despite how pretty they are - is missing the point. Enjoy and experience it, you can always get another!
In summary, can candles expire? Yes it is possible, but why wait and miss out on the experience?! Don't let yours expire, enjoy it today.