2400 mAh batteries (shipped) should provide 5 minutes of vapor draw time. Assuming 15 second "standard" draws, people should get approximately 12 draws per battery—possibly up to 15 draws reliably. This is only a rough guideline; the actual count will depend on technique, condition of the load, and state of the battery. NiMH batteries deteriorate gradually with use, faster if overheated. A smart charger that can perform a conditioning cycle will help to prolong battery life.