NiMH dont have memory, but they do need a c/10 formation charge and or 4 or 5 cycles initially before they come up to full capacity. Also other than the occasional discharge to verify capacity, NiMH batteries dont get any benefit from cycling, infact according to Red its not good for them.

Also, the voltage readout on your transmitter may or may not be the most accurate thing in the world though the ones I have seen that are off are usually off a consistent amount.

One other minor fact to add to the discussion, a synth module will add to the current draw of any transmitter its installed in so a 9c with a synth module will appear to have worse battery performance than another 9c with the same battery and a crystal based module.

Edited to fix technical typo