User blog comment:NecrusIV/Average age of a Space Marine/@comment-1583177-20120817203428

I read on the life sustaining technologies page of the 40k wiki that a human can give for about 400 years if he uses chemical treatments, but my the time he gets that old his body has more or less disowned him and given up. Space marines, being transhuman beings, Id imagine can live for far longer, bear in mind Logan is 700 years old, while Ulrik the Slayer is 900 years old. Dante is 1100 years old (though nobody knows what he looks like behind his mask, he might just be a skull or a Thousand sons style handful of dust in his suit). If your on about when his body gives up and just dies of old age, something like 1000 years would be my bet (with blood angels being something like 1500 years). There isn't any recorded instance of a Marine getting too old for duty and dying of old age, unless its done in secret to protect the myth of space marines being immortal and ever living.

The comments about there being older marines than Dante, you have to be lucky to get to Dante's age, and there may well of been older people than Dante recorded, but at the moment hes the oldest, and nobody knows what condition hes in behind the mask (would be really wierd if he was a necron posing as an astartes, or *gasp* the deciever shard).