Macbook Pro, two external monitors, clamshell mode and heat I use my Macbook Pro 15 (mid 2015) with two Asus PA248Q monitors. It has Intel Pro gpu.

I was just wondering that does it matter heat wise if I keep the lid down?

The hinge seems to have some kid of deflector for the fan so it should push the hot air out.

I was just wondering that can I even stress the Macbook Pro 15 so much that it would cut off and shutdown at emergency heat limit?
From MacBook Pro (Retina, 15-inch, Mid 2015) - Technical Specifications: 


  Operating temperature for the Macbook Pro Mid 2015: 50° to 95° F (10° to 35° C).


You should be able to use it in closed-display mode (a.k.a. closed-clamshell mode) just fine providing the back hinge has a way to dissipate heat appropriately. If it gets too hot, it will auto shut down after the max temperature is reached.