Mandos is not seen as heaven or hell. Like Hades in Greek mythology, there is no 'good or bad' as long as you recognize the gods, so there is no good or bad place to go.
And for the 'if an orc dies', what happens when a tree dies? Orcs are not considered for there own actions, 'free will' may be debatable in this, as they have a choice to kill their buddy or not, but they do not have a choice between good and evil. Orcs should be considered as animals, and not because of their ferocity, but because they are not Children. Dwarves for instance have no proof of what happens to them excpt: The theory of them going back the ground which they sprung from,' which we know they have wemon like every other normal race, and that they think they have a specail place in Mandos for when they help Aule in the rebuilding of Arda. Since neither Aule, Mandos, or Eru said anything of the dwarves afterlife, and they said nothing about Ents or cows anyway, we make the 'afterlife' connection that dwarves are not Children. (We know that anyway) The dwarves are special ina way that they have the Flame Imperishable. I dont see how orcs with the lack of the Flame would have any afterlife to go to, since without the Flame you can not be considered for your well being and actions unto others.
Since we can say nothing about Men's life after death, other than it is good because Eru granted them it, we can not say anything about how a mans life affectes his 'afterlife'.
So what? What i say is this: Without the Flame Imperishable, there is no afterlife for that race because it would be pointless. Wouldnt all orcs go to ha 'hell'? They cant help it because they have no control. And wouldnt all plants go to a heaven? No.
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