These days' computers are pretty smart. They have built-in features that stop charging the battery when it gets to 100%. In a way, stopping at 100% isn't necessary. To explain why this is a good habit, keep in mind that even with these precautions, leaving your laptop plugged in all the time can cause some extra heat, which is bad for the battery in the long run. Plus, it's like training yourself to be aware of how much battery you use, which is useful for times when you can only use battery power.
