I do have one more question. Can you over cool LEDs? Is there an ideal operating temperature?
I guess that's 2 questions.
You CAN overcool LEDs, but their operating range is usually listed in their spec sheet. The ones I use have an operating temp from -30 degrees Celsius (-22F) to 85 degrees Celsius (185F). Barring a Thermoelectric chiller plate (peltier cooling) you're not getting that low, and the energy you're burning keeping them at that temp is so inefficient you may as well be running T8 fluorescent.
Keeping the LED cooler will extend the effective life of the diode, but trying to keep it below ambient room temperature is unnecessary.