Run time measured.
Two days ago I've purchased a new fresh (made at the end of September, 2014) original Samsung battery. Cell made in China, assembled in China. I've measured playback time using a timer application on my Android tablet up to power off due to discharge. The app allowed me to measure the time with a good precision. The result is 7 hours 11 minutes. Firmware v2.1.5-L2, flacs 24/192 compression level 8 (highest), volume 220, high gain, low impedance IEMs (Etymotic HF3), 128GB SanDisk microSD.
There were 6 cycles (turn on-listen-turn off), the longest was 3h26m, the shortest - 2m17s (the last one).
Pisen lasted for around 6 hours past weeks in the same conditions, and the same 7 hours 2-3 months ago. Same result (6 hours) with another, 2-years old, Samsung original battery (Korea-Korea, taken from my test phone at work). Those 6 hours were achieved with 2.1.0-based firmware. So I strongly believe that the decreased time is due to degradation of the cheap battery, not because of the recent changes in the firmware.
One more observation: the new Samsung battery is running significantly cooler than Pisen! Meaning, it has the same sound signature, that Pisen has during the first half an hour, but at the long run. The impression is like Samsung battery has a different sound signature (better SQ)
Please note, that I discharged/charged the battery only 2 times after purchasing and this test was the 3rd discharge, so its performance may become even better in a few days.
Overall, I'm quite satisfied with the result, and I'm very happy that I can purchase a new good brand battery for DX90 so easily, in a local store!