So I bought my CX2 used and it came with cheap batteries for the Spectrum TX that read 5.6 volts. After more then 200 flights I am down to 5.0 and just started to go to 4.9 volts. It seems these batteries last forever! I will replace them once they read 4.9 volts consistantly. Do yours last forever? My old Tx for my RC truck uses 8, has less range and the batteries are only good for about 30 runs.

I still fly a CX (not a CX2) so I use 8 batteries in my Tx. I went to NiMH and just charge them occasionally.
I was going to charge them in the Tx, but the polarity of the plug is backwards so I need to make a gender-bender for the cord. For you that would only equal 4.8 volts. Won't that run the Tx? I know my old 8 cell Tx wants 12v, but it gets 9.6 and that's only until the cells run down a bit.
If you are getting over 200 flights out of 4 AA cells, I don't think you will have to send extra money to anyone to level you carbon footprint. LOL

Yea, The spektrum uses very little power. I bought the expensive lithium AA's from Ever ready, and they are still reading 6.2 Volts after a few dozen flights. I even left it on overnight once.

Don't ever let it get under 5 volts, especially outside, and at 4.5 volts, it is programmed to SHUT OFF! !

True goldslinger, very true!
I wouldnt let them get below 5V either, although i've never reached that as i got my DX7 before that .

Although the CX2 TX's (LP5DSM) are really power-efficient, once there's too little voltage to run the voltage-regulator and fill the capacitors of the 2.4Ghz unit, it'll show some strange and dangerous (for your CX2) behaviour!