From my understanding of animals, lifespan is all based on the speed of its metabolic rate. As endothermic animals, mammals live a high-octane life - growing up fast, being quick on activity regardless of the weather and demanding a lot of food in a short period of time. As a result, they, if you will, "live fast and die young".
Ectotherms such as crocodiles, live life more slowly and leisurely and don't require as much food. However, since they can't create their own body heat, their personalities and environmental choices are limited. Regardless, this leisurely metabolism means that their lifespans get expanded.
Then there's this recent popularity of great whites, tunas and probably dinosaurs being mesothermic, neither warm- nor cold-blooded, but bearing the advantages of both. You can still lead a high-octane life, but your body won't require as much food.
One of the most popular characteristics of fictional hominids - like elves and dwarves - is a lifespan longer than humans. Which metabolism would be better suited for these primates, ectothermy or mesothermy?