Stability Is a System Property
LED performance depends on the chip, package, driver and thermal system. The ceramic substrate is one part of the thermal path; solder interfaces, thermal materials and fixture cooling also matter.
Define Actual Operating Conditions First
Record target current, voltage, ambient temperature and operating time before selection. Rated power alone can overlook complete-fixture limits on output and stability.
Confirm with Samples
Record output and color at thermal equilibrium in the fixture, and compare under consistent test conditions. Model parameters, testing and acceptance are subject to the confirmed datasheet.