I found this recent paper on Peter's blog (thanks!). It's hard to read and lacking some big picture discussion. The study analyzed genetics of 598 elderly people (Calabria, Italy), age range 64 to 105 years. They found a strong correlation of genetic expression of UCP2, UCP3 and UCP4 protein with longevity. What does UCP do and what does that really mean? The following quote attracted my attention:
Recently, Andrews proposed that UCP2 promotes longevity by shifting a cell towards fatty acid fuel utilization thus pointing to a major role of UCP2 in modulating metabolism . This hypothesis is somewhat supported by Barbieri and colleagues  who analyzed the Ala55val polymorphism in a human cohort of elderly subjects from an Italian population.