I know I used to read that it was good to let a lithium battery die all the way once a month or so for battery calibration. Is this still the case? Will it do more harm than good? It will likely be traded in or sold within 2 years but if not, I'm okay with paying for a replacement through Apple. I know Apple considers a charge cycle to be 50% up to 100% (What I read online). I'm curious as it appears my battery sometimes dies much more rapidly even with the exact same use as always. Then it stays at 99% for over two hours. Is the calibration off?