ok, just did a test on XP, same settings as on win7 above.
started playing @ 10:30am on the dot. with battery critical levels set to 3%, it just went into hibernate now @ 16:06
much better than on windows 7 (4hrs 38 min). XP gave 5hrs 36 min.
BUT, win7 didnt dim the screen. hopefully i can get that fixed thanks to another thread and retest under win7 (i prefer it to XP).
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EDIT
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ok, same test as in XP but on win7. same vids played. screen dimmed to 2 bars
started @ 8pm - went to hibernate just a min ago - makes it 5 hours 40 mins. sweet!