there is actually an argument here. If we are asking what is really good for the battery, it really depends. leaving it connected to the adapter all the time will not eat up your charge cycle, so the battery will not deplete. but it will cause the full charge capacity (FCC) to decrease. If u charge it and discharge it all the time, your FCC might not be affected, but if you have ACPP and wants to claim warranty, if your cycle count exceeded the allocated amount, there goes your warranty for the battery. apple says the following though: "Basically, a good rule to thumb is to run on AC power much of the time, but run on battery power for a while a few times per week. Using the battery for 2 full charge cycles per week equates to 300 cycles in 3 years, which is the optimal use." so if the person uses MBP around 6-8 hours a day should keep the adapter plugged and only unplug for a few hours to run it on battery, doing it on a regular basis with "accuracy" so that one can match the ratio of cycle count per week isn`t it a painstaking process? like being constantly on the lookout to check the impending "shrink" of the battery`s lifespan, that seems kinda redundant to me.