Overcharging is not so much of a problem as most
modern laptops have circuitry that keeps the battery just under 100%
when it is plugged in. That means there is less chance of the
battery overheating and catching fire.
However, lithium-ion batteries, like the ones in newer laptops, last
longest when they stay between 20% and 80% capacity. When they spend
a lot of time above and below those percentages, it shortens the
battery's life.
Also, a battery that is charging while the laptop is running will be
hotter than usual. That also shortens the overall battery life.
So, if your laptop is always sitting the same place, it is a good
idea to unplug it every now and then and let the battery take over.
Or you can remove the battery totally and leave it plugged in all
the time.