flickering? hard to say without seeing the actual flickering. Could be a bulb or a ballast going bad. I thought one of mine was flickering the other night and it was water running down the lens.....LOL
It' on the passenger side. It flickers continuously when the low beams are on. also the light is blue as oppose to white. I checked all the wiring and they are secure. The fuse is good. Just need to get it fix because I have no low beams, well almost.
the oem bulbs are UBER expensive, been forever since I saw a price but I wanna say 150 +/- EACH I would do as scott suggested and swap bulbs. If it stays on that headlamp you know its a car problem, if it follows to the other its a bulb problem.
as for replacing both, I have heard of color deterioration after alot of use. but I dont know how noticable it would be if at all, and for the extra cost... you be the judge
I know this might sound like a bad idea but just buy a replacement D1S set off eBay (4300k). They are wicked cheap and produce the same results. They might not last as long, but then again your OEM ones died prematurely as well. Even if they last a year the $20 or so was well worth it. 4300k is stock temperature (white with yellow hint), 5000k bulbs would be white, white. Anything over 6000k is ricey IMO.