It's the power converters that break down from what I've heard, not the LED themselves. So light bulb companies can make the 230V -> 1.5V conversion brittle and have you rebuy lights over and over "as designed".
I've seen a lot of other sorts of failures. On the LED bulbs where individual filaments are visible, sometimes a single filament fails, or flips on and off.
I had one LED bulb that just burned, which was interesting.
I had one LED bulb that just burned, which was interesting.