That would make sense if this were the lifestream. You cannot kill what is already dead. It is not trying to consume us though, so if it is similar it does not carry the same appetite of our own planet.

[And how it wants to reabsorb all those who die back into it. Sephiroth knows that first hand. The planet would certainly break him apart if it could. Luckily his will is far stronger than that.]

But back to what you just said -- have you tested this theory? Of death?