Has anyone noticed this with their xenons? I assume the unit has a vent, I've got to dig out an assembly diagram but thought I'd just ask the group before I start pulling my car apart to investigate.
@Asker - no, it doesn't affect the beam at all, the casing is as close to the lens as you can get and the beam at that point is at its most intense.
@Neil - thanks mate, I suspected it was normal given the physical processes at play but just wanted to be sure. I've not had Xenons before so wasn't sure if this was normal operating behaviour or not. I had seen this before and yes, you're right, it does clear up as temperatures equalise but I hadn't seen it take up quite as large an area of the light before. It's one of those preventative maintenance type questions.

@Mike - awesome, thanks! That answers that question perfectly. Appreciate you going to the trouble of looking that up for me. I've got Elsawin but it's really buggy and unstable. I suspect I didn't get a decent copy. Reminds me, need to get hold of 3.90 which is Feb 2011 current from what I understand.