I've found them to be hit or miss. The key is to do some research on blending EOs. It's more like perfumery than just adding one particular EO to the candle. Different EOs have different "notes", and you need the right blend of top, middle, bottom notes to get the scent to stay strong. I love using them in soy candles, but it can take a long time, and a lot of money, to find a good blend.