Electronic cigarette coils need to be replaced when your unit stops working at its usual high standard. Generally you will notice that it is producing less vapour or the vapour will smell and taste burnt when the coils need replacing. The length of time that your Innokin coils will last will depend greatly on how often you use your electronic cigarette, but on average use four weeks to a month would be about normal. It is important to choose the right coils for your specific Innokin product. Replacing coils with ones that are not compatible means that your unit will not work. In the worst cases you could damage your unit and even create a fire risk. Ensure that you buy genuine parts from an accredited source. If you are unsure about the validity of the coils you have purchased you can check the security number on the Innokin website. The Innokin iClear coils are dual coil heads that will only fit units created to fit a dual coil system. The iTaste uses a similar bottom dual coil system. The dual coil system provides a cleaner taste and is less likely to taint the vapour produced from the liquid. The system is also easier to refill as it is refilled through the base rather than needing to remove the mouthpiece.