I've contemplated water cooling my two 6970s.  I had to re position them due to my roomate not liking the sound/heat in the living room so they are back in my room blazing away at 87+'C at 100% fan. (While being super loud) (I have them overclocked so that each card is pushing 410-420 Mhashes/s, I lose a giant chunk of that hash rate (like 50 per card) if I under clock it to safe temps.

Should I continue running at close to 90'C or...

Would a water cooling set up last me for 5 years~+?  I might bite the bullet on the costs if I can re-use the pump/radiator/hoses for a long time (and only have to exchange blocks).  I often move my computers around a lot (lan parties, etc)  Would water cooling inhibit the moving process?