I also believe that souls live forever and are just sort of 'recycled' into new physical bodies. Many people think they want to live forever because they fear death, and it's a totally understandable fear because there's bloody nothing you can do to stop it from happening. Humans are so used to having control of their bodies in some way that it scares many to think that the control will eventually be taken away.
I don't think I'd want to live forever, or choose to come back after a certain point. The Earth is going to burn up in the sun in about 7 billion years and I would not want to be on the planet when everyone is frying and watching their loved ones die in a fiery armageddon that no one can stop.