What charging mechanism to be used to maximise the battery life? So I got my first Apple laptop, a Retina MacBook Pro. Since macbook pro retina's battery are no longer easily switchable I'm concerned about it's life and would like to maximize it. I have few questions below. 

How long it should be kept in A/C power? Is it okay to keep the laptop connected to A/C power more than 24 hours? Will it not be good for the battery if I keep it in A/C power more than 24 hours?

Is it okay to charge the laptop when the battery reach 75% or should I wait till it goes to 50% or 10%? What's is optimal %?

What's the best charging practices should I follow?
The batteries on all 2012 models self regulate, self calibrate and don't care when you charge them.

You might reduce their total lifespan if you never ever ever take it off charge. Ideally drain it past 20% remaining (better to run it all the way down) once every few months. 

These days, portable batteries are like sealed car batteries. Maybe go in to the shop once a year to have it checked, but otherwise you can forget "caring" for it other than avoiding excessive heat (90 degrees F and up). 

Any time you want, Apple can run extensive diagnostics on your battery (for free at the Genius Bar and also complimentary if you pay for AppleCare.)