Chain life cannot really be measured in miles. Chain life is a function of distance, load, hygiene, lubrication and gearing.
1) Distance: I think that is obvious because it relates to how much the chain was used.
2) Load: this relates to under how much friction the chain enters and exits the various sprockets. It only wears at the moment that it articulates and, increased chain tension increases the amount of friction taking place during articulation.
3) Hygiene: The cleaner the chain, the less grit inside and thus the less friction and wear per articulated movement.
4) Gearing: The smaller the sprocket, the more the chain articulates and the more it wears.
Further, "end of life" is such a vague concept on top of the other variables, that you will get the sort of wildly-fluctuating figures seen in this very thread.