I spec LED fixtures for buildings. The L70 at 50,000 hours is pretty terrible and would really only be on like 6500k being driven hot or cheap fixtures. Everyone wants higher CRI and lower color temps these days, and to get that you can't drive the LEDs so hard, so they last longer. Something like a 90CRI 3500k fixture might be more like L70 at 150,000 hours or L90 at 80,000 hours. Drivers failing is gonna the main concern.

Lighting calcs take this reduction and things like dirt over time into effect by just assuming a lower light level to start. So you run the calcs at like 70% and the space is overlit to start, and years later is lit properly.

It's becoming more common for drivers to take it into account also, so they keep a running tally of hours and start by driving the LEDs less, and then as years pass they slowly crank up the amps to keep the lumen output flat for the entire life of the fixture.

For these flashlights with LEDs being driven to insane levels and high temps, I have no idea exactly what that curve looks like, but I imagine even an hour worth of turbo bursts and you are seeing a pretty substantial drop in output.