I really think Yoda simply dying right before crunch time wasnt all that. They would get on the ship and go different directions to find vader and the emperor. The emperor would be like " Your still alive"! Then Yoda would say a catchy phrase "The force is always alive". Lol im hilarious. Anyways Yoda would be in his dying moments at this time of his natural death approaching. As vader and luke approach Yoda would diminish with the force. Honestly, the emperor and yoda should have atleast met one time in epiosodes 4-6? Come on Lucas your killing me!