Nicotine is a highly addictive stimulant. Since it is present in electronic cigarettes, it can cause you to more alert and energetic. This feeling usually comes about two hours once you have finished using the device and typically lasts between two and six hours. If you are concerned about getting dependent on nicotine, it is recommended that you only use e-juice, which does not contain any nicotine. E-juice is not addictive, and it does not carry any health risks as well.