Any time travel episode past Road To The Multiverse (which wasn't technically time travel anyway) has really been unnecessary at this point. Sure, it was a way to bring back Brian after he died, but was that entire plot-line, little more than a ratings stunt, necessary in the first place? There was no need to have Stewie head back to Da Vinici's time, and really there's almost no reason to ever do another time travel story again because it's been done to death. One final one might be acceptable, but at least take a good long break from time. Blow up the time machine. Break it (okay that's happened a lot). Bury it. Do whatever to it. Just let us forget about it for a while.