If somehow you happen to hear someone said that it’s fine to connect your MacBook battery to power socket all the time, then it’s unlucky that you’ve got the wrong idea. Plugging your battery all the time will shorten your battery life.
Checking Battery Condition
There is an application called Coconut Battery that can help you inspect your battery life.
How is your battery condition?
Fortunately, there is a quick tip that can help you maintain your battery life: by calibrating your battery every month or two.
- Charge the battery until it’s fully charged
- Keep the fully charged state for two hours or more. You may use your MacBook during this time
- Disconnect power adapter
- Use your battery until it goes to sleep (empty state)
- Leave it for five hours or longer until the MacBook’s light stop blinking
- Connect the power adapter and charge the battery until it’s full. Don’t use it in this period of time
Update: Thanks to David for additional information.
Source: Apple Support.