How to Make Your Candles Last Longer
Coat the outside of the candle with varnish. If you hold the candle by the wick you can even dip them in the can. The varnish forms a hard coat which will prevent the wax from running down the outside of the candle.
If that candle is a bit too large to fit into a holder don't whittle it down. Dip the first inch in very hot water for a minute or too. That will soften the wax allowing the candle to slide into the candle holder with a perfect fit!
Other ways to extend the life of a candle
Watch the time. Tunneling occurs when a jar candle is lit for too long. Jar candles should be lit 1 hour for every inch of their thickness. For example, a jar candle t3-inches thick should remain lit no more than 3 hours. Otherwise, the wax on the sides gets higher than the middle, causing it to pool and bury the wick.
Trim the wick. The wick of a candle should be 1/4 of an inch when lit. Before lighting the candle, trim it to this length.
Stick candles in the fridge for a few minutes prior to lighting. It will burn more slowly. This trick can add hours of life to the candle. Don't leave the candles in for too long, as the cold temperature can crack many candles.
Avoid lighting it for long periods. Using candles for 2 to 3 hours maximum will extend the life of the candle.