[ubuntu] Hibernation works only within 2 hours resume?

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http://ubuntuforums.org – Hello all, tried searching but search tool got me! I've got a Dell Inspiron 6400 vintage sunburst (just to say its OLD) and everything is working fine, EXCEPT hibernating, it only works fine if you resume within 2 hours(approx) if you try to do this after a longer period (say after a workday) screen just blinks! Now as far as I know hibernation doesnt use power and just saves state to drive, so what gives? Doesnt matter since computer boots up in like 24 seconds but hey, would like to know if this has been addressed before and any workaround is wisely guarded somewhere. Oh running 12.04, just (Hardware)