The diffuser's adjustable metal grill allows you to control the intensity of fragrance in the car. The diffusion stops just as instantly as it started, leaving no trail, allowing you to choose and change scents as you wish. The cartridges can be kept for up to 3 months after opening, provided the container is properly closed after use. Lifespan of 40 hours continuously, ie up to 80 diffusion cycles (1 cycle corresponding to 1 hour).