While the myriad genetic adaptations, mutations and general mukiness of the Space Marines allows them to live long lives, it is never specifically stated how long a Space Marine will live if he is not slain in battle.
Evidence of their ridiculously long lives is, of course, the current Masters of certain Space Marine legions, Logan Grimnar of the Space Wolves is at least 700 years old, having led the Wolves for that length of time. Dante of the Blood Angels is currently over 1,000 years old, and still kicking ass (see Red Fury by James Swallow).
But there are still more whose lives make even Dante seem like a peach-fuzz ridden child, not counting the Daemon Primarchs who have earned immortality from their patrons, the 13th Company of the Space Wolves, led by Wolf Lord Bulveye, last we heard, has existed since the end of the Horus Heresy.
Now there are certain issues with the passing of the years, since it's entirely possible to enter the warp to travel between stars and find that years, decades, centuries, or in the case of Danarth Lysander, a millenium has passed.
How long can a Space Marine live if something doesnt make a grisly mess of him? Does it ever say in any of the books, or games? If so, which one? This has been a long-standing question between me and a few friends that I managed to get into Warhammer40k, If you have an answer, please, share.