Um...well then, a real-world test for the battery life. It literally just died for me on the bus right now and I've been timing the battery life with my iPhone.
Testing specs:
iPhone 4S (playing Ottmar Liebert's "Up Close" album at 256 kbps V0 LAME MP3) -> FiiO L3 -> C5 (high gain, volume step 4, no bass boost) -> V-MODA Crossfade M-100
This wasn't a straight-on 11-hour listening session, but I turned on/off the iPhone's timer whenever I turned on/off the C5. It's not quite the 14-hour claimed battery life with this test, but still ample for my purposes. I did this test over a course of 2 days with plenty of opportunities to charge the C5 if I wanted to.
The flashing green LED indicating 20 minutes of remaining battery life was pretty accurate though because the bus arrived at my stop at around 20:48 and the LED was flashing at the end of the last listening session (the battery later died at 21:05).