Do Astartes really just deteriorate over time? From the HH novels the opinion of the Marines is that they are functionally immortal; where has this changed? I ask out of real curiosity, not trying to be snarky at all.
I know that the process of making a Marine has become debased and the true meaning lost to mindless repetition and ritual, at least for some Chapters, but has this been shown to reduce the life-expectancy from the HH-era Astartes?
I know that Dante is considered long-lived, an exception amongst even Astartes, but- actually, I'm rambling now. Could someone let me know the fluff-piece that says what life-span Marines can expect? Cheers.