first of all, does brightness change battery life at all? or is it very minor that i shouldn't even bother? 2nd, how do i reset the brightness to the default? i see some settings there but i'm afraid it might reset some other settings as well. can anyone enlighten me w/ some of those resets? lastly, how should i keep the brightness? auto on? bright screen or dark screen? does having iphone bright too much will shorten the life span of the screen? thx.