Constant very high temperatures can definitely damage every component of a computer, especially in a laptop where things are sandwiched together paired up with often inadequate cooling systems. Generally overheating damage over time will show graphic artifacts, programs will crash etc, not just a decrease in FPS.
Things to check:
Your GPU temperature, CPU temperature
Check for updated drivers for both your platform (chipset) and GPU.
Does the ventilation system really seem to be working hard/ high fan speeds?
Are any intake / exhaust ports of the cooling system blocked at all or possibly clogged with dust on the interior?