It will easily run for 3 hours. The following is what I got on mine. I turned the transmitter on and left it on continiously for 3 hours and 10 minutes with the following readings:
Start10 volts, after 25 minutes 9.4 volts, after an hour and 15 minutes 9.3 volts, after 2 hours and 15 minutes 9.2 volts, after 2 hours and 45 minutes 9.1 volts, after 3 hours 8.9 volts. Note that I had complete control of the plane throughout the test. I did turn the receiver off between tests as the reciever battery will not last nearly as long as it is drawing far more current when the servos are being exercised. It is perfectly safe to fly down to 8.8 volts but I stopped at 8.9 volts. The alarm sounded after 3 hours and 15 minutes with the voltage at 8.5 volts. Note that at 9.2 volts, I still had a third of the charge left in the battery. This is with the NiCad battery that came with the unit. I doubt if NiMh will perform quite as well but should come close. If you are charging when voltage falls to 9.8 volts, you are only using a few percent of the energy you have in the battery and unnecessarily limiting yourself.