Easy solution. Install a Voltwatch II. Set it for 6 volt pack and fly. Look at it before and after each flight. When it starts to flicker down in to the yellow, charge it.

With 2700 mah that should last you pretty much all day of normal fying, but with the voltwatch II installed, and if you look at it before and after each flight, well, you are assured that your battery is performing and has an adequate charge for the next flight, OR if it is ready to recharge.

CGr.