The failure mode of LED floodlights. (apparently)

When the lights on my bench came on one of them started flickering in intensity. Initially I thought it was the driver failing, but it turned out that one of the series arrays of LEDs was flickering on and off. It soon stopped, but is now dead. That means the full 20W of power is now being dissipated by the remaining string of 10 LEDs, so I don't think they're going to last too long.
Then I noticed that in the other light where I had used a 50W LED (5 series strings of ten chips in parallel) the middle one had gone out. So now the 20W is being shared amongst four strings which still equates to half their rated current.
But it shows that this appears to be the failure mode of these high power LEDs. Progressive loss of strings in the array with increased burden on the remaining ones. The intensity also drops noticeably as the overdriven LEDs are much less efficient.
So I guess it pays to use the larger wattage LEDs to have some built in redundancy. But it also suggests that you do need to check and possibly change the LEDs in these floodlights now and then.