9 yr old nephew just came out and said, "I have a theory. We die
   everytime we go to sleep but we have a lot of lives. We have
   time limits, just like in Super Mario Bros when you get to 300,
   but then we wake up and get a new life everytime that looks
   almost the same. We have multiple bodies, because when you wake
   up your body is a little different, so your body was replaced
   because you're in a different dimension each time. Your soul
   goes from dimension to dimension, body to body, everytime you go
   to sleep, with most of your memories. When you've run out of
   dimensions, your body timer runs down for the last time, and
   your soul goes back to the first dimension in a new body but
   your memories don't go with you." I guess he's been noticing me
   going onto Philosophy forums lately and decided to give me his
   hypothesis.