Fixture running great since beginning April. Thought an update may be in order. I've added a second power supply allowing me to run each on a different timer to give a simple dawn/dusk scenario. Still no automatic dimming other than that. Added a fourth manual dimmer to allow individual control over each of the 4 different colour LEDs I've used. Two meters provide voltage monitoring through a couple of switches I added. The top voltmeter shows volts for the two left dimmers fed by the 250 watt power supply (Royal Blue & 10000K LEDs on the outer rails). The lower voltmeter monitors the smaller 150 watt power supply (6000K & Blue LEDs on the center rail). By using the DPDT switches I can toggle between monitoring the voltage provided through each of the 4 dimmers. Here's a pic of what it looks like at the moment.
All the 10 watt LEDs should be well 'burned in' by now and the only thing that has failed is one of the heatsink fans. Easy enough to replace since I have a few spares kicking around. Still running without any constant current devices, relying on the dialed down voltage to keep things safe. Intend to do some current measurements to see how things are matched between LEDs, but it's been working so well I wonder why I should bother. If one were going to cook, it surely would have done so by now.