Clue is in the title. At what point does air cooling become a limiting factor?
I'm not talking about extreme OC's that people do just one off to see how high they can go, I'm talking about something that you'll use 24/7. At which stage in an everyday sort of OC do you really need liquid over air?
(Not a rant against liquid cooling btw, I'm just curious. My only foray into overclocking is my Sempron in my sig - I got thinking about the whole liquid vs. air thing because my CPU with a 40% overclock produces only 23-26 degrees under full load)