The life of electronic cigarette liquid depends on a few factors, such as how often you vape, how much you use your electronic cigarette in one sitting, and how much vapor your atomizer or cartomizer produces. My favorite electronic cigarette is the ProVari, which I set to six volts and keep near me at all times while I work at the computer. I tend to take one puff every several minutes, and I find that with my usage pattern I need to buy a new 30 ml bottle of e-liquid about every ten days. I currently use Boge 510 cartomizers and fill them myself from bottles.
If you are thinking about buying a mini electronic cigarette, you will probably be buying your e-liquid in the form of pre-filled cartomizers in packs of five or seven. These cartomizers hold around 1 ml of e-liquid each and deliver around the same total nicotine as a little under one pack of cigarettes. In most cases, you should expect to buy a fresh pack of refill cartomizers for your electronic cigarette about once per week.