if its a good quality, well known brand laptop. you dont have to worry about that. youre playing off the AC adapter not from the battery. charging is separate from usage. only worry about if your laptops cooling/heatsinks are effective during long hours of gaming. the laptop will shutdown itself anyways if it does overheat. and just play on a clean solid surface. and not clog up the airways.
if its not a good quality laptop then make sure you check the temps of your CPU and GPU while gaming. you can download HWinfo or any other OC software that has temp monitoring. overheating from long usage will do irrepairable damage to your internal parts.
if fans are superduper loud and you start seeing lines on your screen, thats critical...