I have some electronics with LED displays/indicators that have been on 24/7 for over 30 years, or 256k hours, and haven't failed. The difference between those and the ones in bulb replacements is that the latter are driven much harder, to the point that they dissipate a lot of heat. Indicator/display LEDs don't get hot or even noticeably above ambient.
Thus it seems that, just like with incandescent bulbs, LEDs will last practically forever if they're run dimly. The difference is that LEDs are actually more efficient at lower current densities, where they're converting more of their input power to light instead of heat, but cost considerations has lead to typical bulbs driving them at much higher currents for more brightness but correspondingly less life and efficiency. They're still far more efficient than incandescents, so I guess that's what counts...
Thus it seems that, just like with incandescent bulbs, LEDs will last practically forever if they're run dimly. The difference is that LEDs are actually more efficient at lower current densities, where they're converting more of their input power to light instead of heat, but cost considerations has lead to typical bulbs driving them at much higher currents for more brightness but correspondingly less life and efficiency. They're still far more efficient than incandescents, so I guess that's what counts...