So I just came across this paper:
http://www.mbio.ncsu...oscar_paper.pdf
And apparently caffeine increases lifespan in yeast through mTor inhibition. A mechanism similar to the one found in humans is credible, given that regular coffee drinkers tend to have the lowest death rates (and also given caffeine's anti-carcinogenic and anti-Parkinson's effects, which may be due to other routes). While it may increase heart attack risk, I think this risk really only applies among those who are already predisposed to having heart attacks.
Now, there's a paper from 1978 called "Effect of caffeine on longevity and reproduction of the housefly", which says that caffeine decreases housefly lifespan. I find this paper VERY interesting because calorie restriction also doesn't increase housefly longevity (what is it that's special in houseflies?)