At what percentage of battery capacity do you start to consider replacing the battery. I'm at 15 months 289 cycles 5190 mAh out of the original 5450 mAh with a 95% capacity. Do I want to wait until it goes down to something like 10%, lower, sooner? If I let it run on the adapter when it goes down completely will I damage my MBP? Just prepairing to know what to do when the time comes. Thanks.