Without knowing how much current (amps) your power system requires, the cell count and capacity of the batteries does not tell you anything about flight time. To use the formula in my post, you need to know how much current your motor-and-prop requires. You might find this information in documentation for your plane or motor, but the best way to find out is to measure it with a wattmeter.

It is never going to hurt your batteries to balance charge them. Balance charging will help to keep the batteries in good shape, but it does not have to be done every time.

- Jeff