I bought a second battery for my MBP and I was wondering what the best way to keep them running at their fullest is. I want them to last as long as they can. I use my MBP mostly for school and on a day where I use my computer a lot, I'll run the first battery dry and then run the second battery to about 60%. If I calibrate the batteries every month, will this be a good system, or should I alter the system? Also, on some days I won't even go through my first battery, along with the second battery just sitting in my laptop bag during the weekends. What's the best system for them?