I just started having this problem as well this past weekend.. I have the stock bulbs in and the right d4s every once in awhile will turn off... but when I switch off the lights and back on it'll come back on but sometimes will go back out again... I hope it doesn't turn off for good anytime soon... I don't want to spend that much money on light bulbs for a car I just got a little over 2 months ago...

 

I have an 07 with stock light bulbs. My drivers side bulb was flickering last night and went off and on like yours.

when i was around 20k miles dealer replaced it for free but now the same headlight is acting up. I wonder if my driver headlight is causing my bulb to burn premature.

My passengers bulb is fine tho.

 

I was wondering the exact same thing you were wondering.. There has to be another reason for it rather than simply replacing them with a higher quality bulb.. right?

 

This could be a ballast issue as well. anyone tried swapping bulbs and see if that worked? Mine went out, tried swapping the bulbs but did the same thing.. luckily I had an old ballast from another IS headlight..swapped the ballast out, it works but it is a little older ballast so works only about 85% of the time when the light turns on automatically. Sometimes bulb doesn't come on switch it off and on again and it'll work. So I'm thinking the ballast is going weak due to age. Dealer wants $1480 for the headlight housing replacement that comes with a new ballast but no bulb don't really want to do that though.
Worst case scenario if I need to replace ballast I'll probably just get a kit and try to wire it in splicing into the factory harness without buying a headlight assembly.

 

This happened to me about a month ago. If not the bulbs, it may be your ballast. You can order a new oem ballast from eBay and have it installed. Good luck