Technically no matter what your soul is going to heaven or hell, it's just your body that dies. Your soul is immortal. Everyone's is. It just comes down to where it's going when it's body dies. Your soul just gets transported to where your new body is. Heaven or hell.
Therefore, we know that the wicked will perish and will be no more! Psalm 37:10 and 20. (Plus John 3:16, Romans 6:23, 2 These 1:9, and many more)
Since we know that the wicked will perish and will be no more, we know that they will not live forever in hell being tortured alive.
When someone is thrown into gehenna, their soul and body both die (Matt 10:28); and just prior to that, God kills them (Luke 12:5). James 5:20 says that to turn a person from sin will "save their soul from death." John 3:16 says that we're given "eternal life" instead of "perishing" -- and what does it mean to "perish"? To stop living, or to die. Genesis 3:22 says that God banned man from getting the Tree of Life so that he wouldn't "live forever."
The soul that sins will die; the wages of sin is death; but those who believe in Christ will live forever, as a free gift from God of what He alone has always owned: life.
I sent the response 'Jesus conquered death for us'. You either go to Heaven or Hell (your choice, pretty much). Annihilationism is false doctrine. Please go here- it should answer your question with more clarity and detail: http://www.gotquestions.org/annihilationism.html
This site has helped me with other questions I've had before and I'm sure it'll help you as well.