No problem. What you were told about the batteries is pretty much true. Going lower than 3v per cell can permanently ruin the battery and render it useless. Look around for a voltage alarm, It will give off an audible sound when you approach the limit or a signal you with a blinking led. Most people time there flights and gauge that against how much voltage is left in the battery. General rule of thumb is to land as soon as you notice a performance drop in the heli.