It depends on the LED lamp you use.
Some are just like CFLs and hold the same power and go up in temperature and fail prematurely or downright blow up depending on how much it overheats.
Some dimmable LEDs exploit dimming capabilities using temperature sensor input to force dimming to hide their inability to sustain claimed output without damage for long. So, they operate at full output and once it hits the temperature set point, it throttles down the output to avoid the self destruction of LED or ballast. While it can avoid down time, it also hinders the discovery of LED installations not living up to performance expectations
hmy:
It all depends on the fixture size and design. The worst ones are jelly jars and pucks. Pucks are insulated with a foiled fiberglass on the top to protect the ceiling. Heat rises. If the fixture is rather large, there's room above the lamp and it's not mounted base up, convection current does its magic. Heat rises and away from the ballast, air within the fixture circulates.