Trim your candle wicks nicely in between burns. While the candle is burning, carbon builds up on the wick. If you continue to light the wicks without trimming, the flames will get bigger and burn faster. This is why it is essential to trim your candle wicks to 1/8"-1/4" before every burn.
In other words, to get the BEST performing candle, make sure you have a wick trimmer!