It is the same question again!!!!!!
1. Macbook has its own mechanism/chips to detect your battery level
2. Once it is fully charged, it stops charging it
3. Battery in fact stays fully charged for some time and then once it starts to lose battery again for up to around 4 %, the macbook would charge it again.
(this takes a month to lose battery)
4. To maintain your battery, u shouldn't let it fully charged all the time (like a year). Every month, deliberately use up its battery down to 20% and fully charge it again, to keep the ION inside the battery mobile.
5. Keep the plug all the time. There's no need to worry this stupid question anymore. As a matter of fact, this applies to all new Notebooks