[wutangclan]

I have a 2012 E91 LCI (328i Wagon/Estate) with Xenon HID headlamps.

My daily commute consists of a ~30 minute drive that starts and ends inside a parkade. Thus, if the headlamps are set to AUTOMATIC, they will come on twice during my commute, and only briefly at that. I rarely use the high beams (aka flash to pass).

So, my question is: what will be better for long-term bulb/ballast life: to leave the headlamp switch in AUTOMATIC or ON? I am lazy, so I just want to leave it in one or the other all the time. The car is smart enough to turn off all lights when ignition is off even when the switch is in the ON position, so draining the battery is not a concern.