Do you think hell is to create more demons for Lucifer's army? Think about it, you would have to get used to eternal suffering eventually, the physical and emotional pain/torture can only go so high that any higher would feel the same. It would toughen you up, make you stronger, more resilient, you would be twisted into the perfect weapon, a soldier that would make even the Spartans jealous. Is there any being more dangerous than one that fears and feels nothing? Unless they just wipe your memory every now and then but would that not defeat the purpose of experiencing eternity?