Jumping the Shark
I had this discussion before the American Elf comic went out last week with my friend and ex-roommate, Steve. It went more or less like the first half of the comic. I stand by what I said, regarding time travel, scifi, and jumping the shark.
Some scifi is based off of time travel, this is always risky. Not only can time travel be confusing, but it has a great potential to be flat out wrong. This happens all the time yielding paradox after paradox. Introducing it late in the game seems to be more a matter of trying to create new gimmicks and scenery. Take the movie Teenage Mutant Ninja Turtles 3: Turtles in Time, obviously a jump of the shark. Lost had lost its plot when it unveiled time travel.
Star Trek: TNG, DS9, and Voyager, though I'm a fan, did this all too often to generate bit content. While I'm a big Trekkie, and ingeneral a huge dork, Star Trek has mixed all sorts of time travel, not for plot development, but as filler. With little warning they''ll be in the past as just an excuse for new costumes and an unimportant story line, that winds up not changing the plot at all.
All of this said, the latest Star Trek reboot movie was actually well done in my opinion. I can't wait for the next one. I'm also looking forward to Looper. Some scifi based on time travel will be done right.