"These liquid-cooling systems, which were designed by Delphi, manufactured in Mexico, and shipped to Apple's manufacturing facilities in Asia, have been the topic of concern at several Apple exec meetings.

According to reliable sources, Delphi only guarantees the cooling systems to Apple for a period of 2.5 years, though the expected life-span of each unit is rumored to be closer to 2 years. Sources say the lifespan is limited by potenial leakage of the thermal conductive fluid inside the systems. Apple reportedly fears the fluid could cause damage to consumer's valuables or expensive carpets, which would leave the company exposted to potential lawsuits."

http://www.appleinsider.com/article.php?id=993