Typically it’s not the emitters – the LED’s themselves – that fail. If driven correctly, those have lifetimes of tens of thousands of hours.

LED “bulbs,” the type that replace filament bulbs in consumer fixtures, typically fail in their driver hardware. LED’s run off of low voltage DC and in the base of all of those LED conversion bulbs is a power conversion assembly that steps down and rectifies 120v/240c AC to whatever DC voltage the LED array in there expects. These are inevitably made out of whatever the cheapest passives and semiconductor components the manufacturer thinks they can get away with.

The main killer for all semiconductor electronics, which includes both LED’s themselves and their driver circuitry, is heat. This is often exacerbated by the fact that LED replacement modules are usually stuck in enclosed light fixtures designed for filament bulbs that have insufficient ventilation to get rid of the waste heat from the components in an LED module. The insides of those enclosed ceiling light fixtures, the ubiquitous “boob light,” gets hot, even with only LED modules installed. Filament bulbs don’t care because they don’t have any electronics in them and how they work is literally by getting so hot the glow. But LED modules in that kind of environment will invariably suffer an early failure.