>  I currently have 6 customers with over 200k on their engines. Just saying it is possible. The real trick is that it was never overheated. From my experience, almost all water boxer failures were due to an outside influence. Lost belts, hoses, fan not working, abuse, etc. 

Reminds me of that essay on the "Deutsch Method" for automotive
maintenance-- vigilant inspection of all running gear and prompt
repair of any deficiencies. Wasserboxers seem like they can withstand
tremendous punishment, but only if they're running properly. The
design appears to be such that neglect and abuse drastically affect
durability. With regard to (for example) the head gasket surface
corrosion sensitivity, an automotive engineer for GM might ask "what
happens when the owner continually ignores a water leak and just keeps
dumping tap water in the cooling system?" I imagine the German
engineer would get a startled look on his face and say "WHY would
anyone DO that?"
-- 
John Bange
'90 Vanagon
"Keine Bange, wir holen die Zange!"