I, personally, think the answer is (shudder) to error on the long side with regard to default backlight brightness. Also to error on the memory-hogging side with regard to dircache.
I think the best thing to do would be to create a simple "Battery Life FAQ" in the manual explaining steps users can take to, well, lengthen battery life. Ship for UI performance and teach them how to tweak for battery performance, IMHO. --Soap
