I have a 3GS that I just bought used and I believe it's around 1.5yrs old. I've been having some pretty poor battery life and the first thing I want to do is recalibrate the battery. Should I simply fully charge it tonight and then continue to use it until it shuts itself off? I figured I'd run some movies or something towards the end of the night to accomplish this. Is there anything else to do besides that? And is just one night all that's needed? From there forward, I'll simply charge it every night regardless of the battery left... Oh and I'm on 4.2.1 if it matters.