From the sound of it, you can think of the ghost as your soul, with the exception that it's a physical entity. so as long as you have your "soul" you can never truely die. your ghost dies, you die. Another way to think about it is as a puppet. If your puppeteer (Ghost) is captured or killed, there's nothing to give the puppet (you) life. age wise, no. bodies will still deteriorate into dust eventually. maybe an Exo could, but parts might need to be replaced, which might throw off the ghost.