Board Thread:Warhammer 40k General Discussion/@comment-24383134-20140105071847/@comment-6078851-20140105162037

there's a few sources which state that astartes are effectively immortal, the irony being that no-one knows how long they might live for because, while effectively immortal, they are all destined to die in battle.

they don't suffer from (non-chaos) illness but they do age. ageing is the degredation of cells, so if their cells degrade then they don't have indefinite renewel. this would imply that they aren't immortal but only exceptionally long-lived.

if vulkan is still alive then that would make him the oldest in the imperium, barr the emperor (i discount bjorn because don't dreadnoughts spend most of their downtime in stasis?), and would be indicative of how long astartes may live for.

personally i would like to think that astartes are immortal in terms of ageing but unless one decides to become a peace-activist and spends the rest of his life away from violence (and potential death) then we will never know for sure.