I’ve seen some of the newer halo kits for Infinitis, BMW, etc. using the CCFLs.
But that’s a good point about lifespan and temperature threshold. Glad you mentioned it, because I’ve never seen a LED burnout or an inverter blow - however, CCFL vendors say, on average, 30-50,000 hours of continuous use. That’s still quite a while. But it’s still glass; one crack and that’s it.
It depends what company you go with in terms of dealing with temperature. Basically, don’t go with Crappy McNobody cough ebay
Here’s a good site I found:
http://www.lite-eyes.com/
amazing stuff 
The above site/vendor is quoted from a thread:
The CCFL light is made of glass. The protective housing is made of a high heat durable plastic. The Lite Eyes CCFL Halos/Angel Eyes are guaranteed to be waterproof, shock resistant, and heat resistant. The CCFL ring, protective housing, and inverter will not melt, distort, or burn out from high temperatures (unlike the LED counterpart). There is a full lifetime warranty on the lights as well. This is a high quality product that is professionally made.
There’s cheaper out there but, of course the results will vary. And for the record ebay has lots of high quality stuff, but it’s swimming in a sea of rubbish. you just have to search well 
This was what I always knew of how to make a halo. LEDs + slatted clear plastic. pretty simple. but yeah, CCFLs are getting a lot more rep now. They’re pretty bright and can be a bit more uniform. But there’s some great ideas like using reflective tape behind the LED halo to make it about perfect. This guy did a good job:
http://video.google.com/videoplay?docid=-2758135885592309829&hl=en