Jblane: I'm not sure if it's related at all to Location (e.g. weather or temp).. but the OLD EJ25 DOHC 1997-1998 was a horror show. you could set your watch by the headgaskets going at 60,000-70,000 miles. (From my communication with some rally guys apparently even JDM cars of that vintage were the same) The SOHC EJ25 solved most, if not all of those issues, but I have seen 2 so far early (02-03) 2.0 wrx DOHC motors let go too, one just in June at a rallycross.. some early 2.2 turbo kitted cars I did were hard on gaskets too.

and I personally cooked a loaned early 2.5RS during a rally. funny thing is 4 years later that same exact 2.5RS came into my shop for another engine, which we thankfully had in stock, and rebuilt with the then "new" gaskets

you are right I thought the multi-peice coated gaskets were the holy grail in solving that problem, but apparently subaru felt it required to beef up the the 2.5 turbo cars. I thought this was in direct response to more Headgasket issues, but I have been VERY removed from any subaru work for nearly 6 years, so please take it with a grain of salt. I've never turned a wrench on a USDM STi engine so I cannot comment with 100% confidence, Now give me an EA82t and we can talk