Do HID's dim over time?
 

I had my car in for maintenance and noticed that the headlights in the Q50 loaner were significantly better than my 2013. Do the HID bulbs lose brightness over time or does the Q50 just have better headlights?

Yes they do. If you ever replace just one side with an identical bulb after they've been used a year or two, you will see a distinct difference. I don't know if it's actually dimmer per se, but the color isn't the same.

Good, so I'm not crazy thinking my headlights were brighter when i purchaced the car a year and a half ago. Anyone know the difference in output after X hours in use?

Q50 has led headlights which are brighter than hids.....chances are your 2013 hids are fine, you just aren't used to the brightness of leds

I was under the impression that the Q50 LEDs actually had a lower lumen output than G37 HIDs. Maybe just a better design?

It may be a combination of the bulbs being slightly dimmer, and possibly some yellowing of your headlight lenses?

They aren't as bright, but the cooler temperature makes them appear as though they are.

Our G37 sedan projectors are one of the better projectors out there.