JXD s601 & Yinlips YDPG16 have been reported to be in the 6h and 5h runtime range for gaming. I really don't think that the A320 or the other would last much longer under heavy gaming given the less power efficient SoC used in two of them and smaller batteries.
I pretty well expect that most of these Android/ARM based handheld consoles will last in the 5h range which is actually not too bad, but it'd be better IF they had user replaceable batts like just about every single smartphone, a few tablets tablets, and a few handheld consoles.
Also if you're deadset on less recent hw, there's also the gamegadget which has the Ingenics 4750 SoC which is SLIGHTLY better than what's in the Dingoo's w/MIPS SoCs. (Would've been interested in this had they gone with the 1GHz Soc WITH a GPU... 4760? or maybe it was 4780? It's been so long that I looked at them that I've forgotten...)