User blog comment:Omega natsu2/Fairy Tail Episode 206: Panic of Library, Review./@comment-83.255.195.39-20141101042014/@comment-7418318-20141101093147

I don't really see a problem with the timing... maybe with the way it was cut together, but not the actual timing.

If we assume that Natsu fought for say 10 mintues, that would make 90 minutes in the Human World. Considering that while Natsu was fighting, Lucy & Co were able to go all the way to the library and read whole stacks of books, the timing seems to work out fine.

As for the matter of "falling" out of the Spirit World I have couple of theories.

In the last episode they did say that the unusual weather was caused by the Celestial Spirit World and Human World blending together. Maybe that created areas where one can slip through into the other world.

Or it might have something to do with Virgo. Natsu was falling through at the very moment where Virgo was lighting up when she focussed all her power. Maybe calling all that power from the Spirit World weakened the already weakened borders between the worlds to a degree that Natsu could pass through.

With Spirits being naturally drawn back into their own world, I wouldn't be surprised if there's also a force that pull Humans back to their own world, even if it's usually not strong enough by itself to bring them back.