When you are a Mac Book/Pro user watch your cycle count meaning how often your battery has recharged. You should use your battery here and then otherwise the battery lifetime decreases rough. My wife didn’t use the battery for a longer time and the battery performance was a mess. Apple support wanted to know the cycle count which was low and said: “Of course you have to use it frequently, oh and yes, this is in no manual and you get no exchange”.
System Profiler (Apple->About this Mac->More Info…)->Hardware->Power->Health Information.
My cycle count is 62 and condition “good” though which is ok for my 3 month old laptop.