Should I keep my notebook's battery fully charged when there's an outlet around?

I've read that having the battery fully charged whenever possible prevents unnecessary wear and tear. In fact, the source claims that letting the battery discharge to then recharge it is very bad.
Added (1). I have contacted Lenovo Support and have been told "[…] if you have conservation mode enabled, you can leave the charger plugged in. Because the computer will stop charging once its at 60%, this prevents the battery from being overcharged."

Read more: Should I keep my notebook's battery fully charged when there's an outlet around?