Hi, i just bought a new 15" mbp after my 2008 model died (motherboard) I use it 90% of the time with external cinema display 23"(no power plug for mbp) external keyboard, mouse etc,... So because of the external display i have to keep the laptop powered all the time. I have been told it kills the battery. So what to do? Disconnect the laptop and discharge the battery completely once a month? Thank you for your advises!