That's a nice set of questions.
"If they are dead then the light we see at night is just an image of what once was?"
Yes, that's true for some distant stars.
"When will this light finally reach its end or does it just keep going on for infinity and traveling until it hits something where it either gets absorded or bounces back off into space."
If we understand things correctly, the light just keeps traveling until it gets absorbed by some other star or planet or dust or something.
"will the big dipper and all the other constellations one day not exsist"
Yes, none of the stars we now see will continue forever as active stars. They use up their nuclear fuel after a while.
"what lifetime does anyone expect that to be." It varies between stars but typically is something in the range of roughly 10 billion years.
(published on 02/08/2012)