User blog comment:Mohrpheus/Spiritual Imbalance in Bleach - The End of the World?!/@comment-1932702-20100901104153/@comment-1712587-20100901131351

That's another very good point about the shinigami life expectancy, can we make the assumption that all souls live longer in SS? not just spiritually powerful ones, i would base this on the fact that Renji and Rukia didn't grow up any slower than their friends. therefore there should be a constant surge of souls as humans constantly cross over into SS since they live a fraction of the time a soul does.

of course all of this misses out the fact that if in life a human soul does terrible deeds they go to hell and are also struck out of the equation!!!