"I'll give you the definition of immortality from a Melchizedek point of view, which hopefully will help. Somebody else may have a different definition, but this is what we feel. Immortality has nothing to do with living in the same body forever. You're going to live forever anyway; you have always been alive and you always will be, but you might not be conscious during all that time. The definition from our point of view has to do with memory. When you become immortal, you reach the point where your memory remains intact from then on. In other words, you're conscious from then on, with no unconsciousness coming in. It means you stay in the body as long as you want to,and when you want to leave it, you leave. To have to stay in a single body forever would be a jail or a trap, because it means you couldn't leave. There might be a reason for leaving that body, and you will eventually find that you don't want to go beyond wherever you are. This is the definition of eternal life: Simply put, you have continuous, unbroken memory."
Source:The Ancient Secrets of the Flower of Life by Drunvalo Melchizedek pages 143-144.