One of my favorite SF tropes is the "long path": involving time travel, either when one character goes forward in time instantaneously and the other character has to wait out time like normal, or when one character goes back to the past and has to wait for the present to "come again". I just love playing around with time like that. Couple it with an immortal character for even more mind-blowing time journeying. Two good works for reference are Doctor Who (especially the Steven Moffat era) and the Hitchhiker's series (poor Marvin).