For LEDs, it depends on the amount of heat, but usually decorative LEDs (LED ropes/strips, etc. but not those ultra-bright panels) aren't using the type that generate that much heat, and if they dim, it's usually because the manufacturing is low-quality to begin with. Headlamps and flashlights are different as they usually comprise LEDs that each use order of watts per LED, and they're attached to star-shaped mounting heatsink plates to fix to heatsinks. That UV LED I bought needed a special heatsink with a heat-pipe in it to remove the heat without active (fan) cooling.
"The essence of tyranny is not iron law. It is capricious law." -- Christopher Hitchens
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