Here's a tip that might help, especially with soy candles. The first burn is the most critical it creates what's call the "candle memory", so it's important to let it burn/pool all the way to the edge to prevent tunneling. When a candle has this imprint to go off of the, you'll get the most out of its life. Also, trim wicking is imperative! I recommend BRENNAN CANDLES from Colorado.
Put new candles in icebox for 3 to 6hrs. They will burn slower and to the rim. Also for emergency candles that burn 72plus hrs take jelly or mason jars. Fill with (crisco type grease fat Crisco oil not the liquid kind the solid kind your granny used) or off brand. Warm slightly, add fragrance or herb oils to scent. Freeze to solid (shaking occassionally to spread fragrange). Take out freezer, buy birthday candles or thin, cut to height of emergency candle, push down in center of candle. Voila. If you use a wide container, place 3 candles, in triangle, also burns brighter with 3 and all are smokeless.