you should keep your laptop cool while playing games , because a hot laptop breaks more quickly and it also affects the battery life-span.
If you always use your laptop on your thigh, then the hot laptop will give you serious health issues.
(I always use a cooler when using my laptop, and when I can't find my cooler, I simply put five blocks of about 1.5" high under the laptop, to have better ventilation, and have the fan(portable fan with short stand) blow towards the laptop from a safe distance.)
You can always check if your graphics card or CPU is very hot by using the following softwares :CPU-ZGPU-Z
It is best to stop
playing if the temperature of the GPU(Graphics Card) Or CPU exceeds 80'c .