I guess I know what Qx is thinking about. From LED-bulbs we know that they are lasting 25.000h - printed in their specs. But finally - looking at my bulbs at home, some were gone after one year. All light emitting semiconductors have a limited lifetime. This has something to do with the mobility of ions inside the structures.

But: The main problem in these LED bulbs is not the semiconductor itself, but the electronic parts supporting the light emitter. Often there are flimsy low cost parts worth less then one cent limiting the lifetime of the whole system.

Second: the biggest problem for the lifetime of LEDs are high current (ESD-discharges) and the heat generated in the LED-chip, which has to be cooled away to protect the chip. If a VCSEL is running at low temperature (<40°C) and low current (<1 mA) it probably will last forever.

But finally this has to be tested.