It depends on the capacity of the battery. I was using a 4.8v 2300mah battery pack all summer long, and it could realistically fly for a FULL day. I'd fly in the morning, leave my plane at the field, and fly in the evening. My voltwatch never went below the first yellow bulb, if it even made it to yellow. Not sure how many flights, but a whole gallon of fuel with a .46 engine.

There are batteries that are only a few hundred mah, like the ones the come with radios. They only get a handful of flights (5?) before needing a recharge.