I had backpacked my quad, gopro, transmitter and 5 batteries down a long trail for some shots of a rebuilt train trestle. After two quad batteries my tx starts beeping and I couldnt figure what was doing it. Set all the controls to neutral etc, no help. Then I got it, after 5 months of flying 27 times, going through 194 battery changes for about 1200 minutes of flying time I finally had worn out the tx batteries (which are rechargable NiMH). I actually carry a spare set of AAs in my kit box which of course I left in my car since the tx batteries never seem to die. I figure between the warmup time and battery changes when the tx is on, numerous calibrations on the PC when the tx is on, and flying time I got about 1500 minutes of time from a set of rechargable AA. So if you, like me, are going on five months of flying time at about 2-4 times a week, five batteries at a time, then get ready for a new set! You don't want the tx going down without ample warning. No sad ending thankfully to this story except unused quad batteries and a wasted trek into the woods, for now. But I think a lot of us got our Phantoms at near the same time in the spring so heads up on the tx.