i read somewhere that LEDs are overvoltage-sensitive. if they are given more than their rated voltage, they glow much brighter, but their lives are drastically shortened..
someone recommended somewhere in this forum, an off-the-shelf solid-state voltage regulator to maintain correct voltage..
you can connect two similar led's in series. para maging equal ang voltage across the leds, install a resistor in parallel with each led.
to increase their life expectancy, a more complicated way is to parallel the 24v leds with a 1watt, 24v zener diode with a series resistor. the value of the resistor depends on the led current. ipagawa mo na lang sa experts.