Ahh! No! Driving high power LEDs with a constant voltage is not a recommended practice.
As long as the voltage is within spec AND the current is within spec, then the life expectancy will be within spec.
Is this true? I thought LEDs are not current limiting devices. I assume that the fact that these are 10W LEDs means "don't drive them over 10 watts" not "the LED will self-limit to 10 watts".
I wasn't quite specific enough...not current limiting. Just equivalent resistance @ 12V.
An ammeter would be useful to check the rate of current rise .. it won't register until you get near 9V, then it will climb to 1.05A as the voltage increases towards 12V.