bigda...., the length of time your transmitter works is no indication of how long the receiver battery will sustain flight. The receiver under typical use will probably draw much more current than the transmitter does, especially if you have many servos and do lots of manuvering. Current drain on a typical servo can be as high as .5 amperes (500 milliamperes) durring maximum load and will most probably each draw 25 to 50 milliamperes just sitting doing little or nothing. The receiver will draw about 30 milliamperes all the time it is on. The suggestion to use a Voltwatch or equivalent is excellent, much better than a meter as you can check it at the end of each flight before you turn off the receiver and transmitter, to get a good actual condition of your batteries; much better than an expanded scale voltmeter.