(which, considering the horcruxes and the spell which can restore him to his original state, is probably not so unavoidable as he implied.)
While he’s certainly determined to make Harry believe he’s going to die (“this is the last time I will be able to do this for you”), it is likely he is lying for a couple of additional reasons. The man obsessed with not dying, prepared to tear his very soul to shreds to stay alive, has
a) been trying to prevent Harry from seeking a way to bring back the dead, and
b) been doing so purely as part of an effort to save the world—which he has no reason to care about unless he expects to remain in it.
a) been trying to prevent Harry from seeking a way to bring back the dead
If Quirrell is going through time by using up bodies and moving to new ones, applying a bring “back from death” spell to a former host might force him back to his previous used up body.
While he’s certainly determined to make Harry believe he’s going to die (“this is the last time I will be able to do this for you”), it is likely he is lying for a couple of additional reasons. The man obsessed with not dying, prepared to tear his very soul to shreds to stay alive, has
a) been trying to prevent Harry from seeking a way to bring back the dead, and
b) been doing so purely as part of an effort to save the world—which he has no reason to care about unless he expects to remain in it.
If Quirrell is going through time by using up bodies and moving to new ones, applying a bring “back from death” spell to a former host might force him back to his previous used up body.