Pr our modern human standard we view eternal life as an idividual person continues life, outside the bounders of life and death. However if we view this on the material level the concept of eternal life changes. We are all made of cells and when our DNA tells us that our time is up we will die. From this point onward of death we start to decompose and become energy contained inside the form of dirt.
Now, if we follow this circle around the plants/animels/insects will consume dirt and absorb the energy/vitamins/minirals that we, were made of. These plants/animels are then consumed by us, the human race. As such, we could be considerd immortal by the diffinition of our circle of life, so to speak.
Then when two the two sex's join to create a form of young, part of that energy/minirals that you and I were made of, would be used to create new protin chains, new cells and such, creating a new idividual and thus the cycle has ended. You could consider yourself immortal by this.
I'd still go with living 500 years if I could, getting killed and eaten would't get any chicks.