"How often do you have to charge it, and how long does it last?"
The Firefly has a rechargeable battery. The Firefly 2 battery is USB 3.0 compatible and advertised to deliver between 40-80 draws. In one test, it delivered approximately 40 long draws, each averaging 30 seconds. It powers a 50W heater and heats rapidly, in approximately 3-5 seconds, depending on the temperature setting (there are 6). Charging time is around 45 minutes, and the device comes with 2 batteries and a charging dock.
The Firefly 2 battery is a rechargeable and replaceable 7.4V Li-lon that provides a Quickcharge CA adapter that charges within 45 minutes. Can be used up to 40-80 hits varies on intensity of the hits and heat set temperatures.