The LED lightbulbs should use less power (sure) and work for years (not quite). At least 20.000 hours - that would be almost 10 years at 6 hours a day. But I see many of those die after a month or two. They flicker or seem completely dead. Why? What can be done?

Looking inside it becomes clear that the LEDs die of heat. There is not enough thermal paste. The power supply with BP 3122 IC is fine in most cases. Still, it is easy to repair these bulbs with 4 x 1W Power-LEDs by exchanging them from the broken ones. You can find the broken LED with a lab power supply set to 3V, 50 mA (normal operation: ca. 3.3V, 300 mA per LED). + and - are marked on the PCB, marker pen helps. You'll need a good soldering iron, much heat and some patience to replace the LED. Apply ample thermal paste. I have tested them for a few hours with an isolating transformer before I put them to normal operation.