lee730: FLAC requires more processing from the Rockchip DSP, so 4hrs is not unreasonable. What takes HUGE amounts of power is DC-DC switching (step-up power conversion). This is one main reason the unit runs so warm (and may very well be root agent for this device's horrible reliability).
BTW ... I don't have an iPhone, iPod Touch or any of the new-style cell/mobile phone devices (similar to the S:Flo2/Teclast device). How do warm do, e.g., the iPhone, iPod Touch, etc. usually run? Compare/contrast to S:Flo2/Teclast please -- thanks!
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The iPhone 4 can get pretty hot itself while making Phone calls and more so when in a warm place such as your pocket. I haven't noticed it getting hot though while listening to music, and the battery life for music is very impressive on the iPhone. I think it's over 30 hours.
And regarding the player lasting 4 hours, if others are getting double my playing times on flac files as well, something isn't right. I sent in an RMA to MP4NATION and it seems they are going to replace the player with a new one. They just requested for some pictures of the warped USB port. Since my camera is pretty good I took some photos of the front screen. Zooming into the picture you can see the sand in-beaded into the screen. So my experience with this company has so far been a pretty decent one. I would highly recommend doing business with them. But I haven't experienced the issues that others posters have mentioned earlier. I assume they spread themselves to thin at that point, but they were trying (I think).
Below is a link to a few pictures to show the damage on the S:flo2. If you click to view the picture it will allow you to zoom into the picture giving you a much clearer idea of what I am describing.
[URL=http://www.head-fi.org/image/id/1328086/width/1000/height/800][/URL]