There are a few factors to consider when selecting a flameless candle. The most important consideration is the distance the flame needs to reach from the wick in order to create heat. A candle that is placed close to a heat source such as a stove or oven will require a longer flame time in order to reach its target temperature, while a candle placed far away from an heat source will have a shorter flame time and will be more easily lit. Another important factor is the type of wick used. A wire wick will need to be replaced often due to heat damage, while a ceramic or plastic wick will not react as quickly to heat and may last longer.