I burn them in the evening when I'm relaxing, I burn them at mealtimes, and I burn them in the bathroom. Pop candles into the fridge for an hour before lighting them, but wrap them in foil or cling-film first to prevent the wicks from absorbing moisture. When burning pillar candles, let them burn long enough each time to create a pool of wax that almost covers the diameter of the candle. This will ensure that the candle burns evenly each time you light it. If it doesn't create a large enough pool you'll end up with a tunnel through the candle and eventually it will either melt through one side, or you'll no longer be able to light it.
Draughts create a larger flame and uneven burning.
They will fade the colour, and if left for too long, the candles will bend. - If your candle is too slim to fit snugly into the holder, wrap cooking foil or tissue paper around the bottom of the candle to make the base thicker. Don't worry, the tissue paper won't burn even if you do allow the candle to burn right down into the holder, as the melted wax will soak the paper. If you only have the uncovered type, pour some water into the holder before lighting the candle. When it's extinguished and the wax has hardened, it should be easier to pop it out of the container. Once hard, cover the area with brown paper and gently press with a warm iron.