Depending on your playing style the battery life will vary. On average, the estimated battery life is around 8 hours. 

We recommend using AA batteries designed for high-current devices. Our favorite is the Panasonic Eneloop Pro 2450 mAh

Don't mix different batteries in a device which takes more than one battery.

Alkaline cells tend to leak when a potential voltage is applied. i.e., when you try to charge them or a low current battery is mixed with a new battery

This can happen in devices with more than one cell in series if some of the cells have less capacity than others. 

This is why one should never mix cells by type, brand or age in devices where the batteries are run in series.