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-ZIt is best to
stop playing if the temperature of the GPU(Graphics Card) Or CPU exceeds 80'c .
Regards,
haroon1992