aircooled vs. oil cooled vs. water cooled turbos?

[sdturbo]

Who on here has ever seen a turbo that has died from coking? Granted it has happned but not something anywhere close to common. I might have seen a few 300+k mile volvos at the junk yard with seized up turbos that could be coking but they have probably been leaking through the seals for 100k. Those kind of miles are way beyond the service life that any moded car will see and they are water cooled anyway.