

The LED bulb itself is not typically the reason that these fail. There’s also complex regulation circuitry which consists of far more complex components than a single LED. Electrolytic capacitors and driver circuits can have shorter lifetimes than the actual bulb.
With that said, manufacturers know this, so they also tend to overdrive lower cost LEDs to bring the failure rates in line with the rest of the circuit. This sounds like this may be what has happened to you just based on the dimming, but without knowing exactly how they have wired it up, it’s difficult to be sure.











They don’t need to run failure studies. That basic characterization work is mostly already done for you. Component vendors (should) publish tables of mean time between failure for the components you’re buying that can be used to get a rough estimation with just a few minutes of effort. Typically it’s indexed by temperature, like for caps, but depends on the part.
Now, does the bottom of the market actually use those tables? I can’t say for sure. I know one high power headlamp company does this for their LED drivers to balance lifetime with output, but I can’t know for sure what every business does.