My cousin and I were debating over this last night. I unplug my laptop once it is fully charge and he said that leaving it plugged in after it is charged isn’t what damages the battery but it is charging it before the battery is low. What do you think/know? I am a college student and would like this (brand new) battery to last me for at least the next four years.

Charging it before the battery is low, is not a problem, and neither is leaving it plugged in once it has charged. It should switch over to AC power once it has charged. Rechargeable batteries can only be recharged so many times. Your best bet for keeping your battery for 4 years is to not use it that much. Use AC power when ever possible!