I thought it was just a few day's voyage. The narrow sea is like 2 days maybe + maybe 5 in slavers Bay?
i really have no idea. just noticed that the dragons were about 5x faster. maybe there are islands where they can stop and wait for the boats to catch up.
that'd be great if a storm killed dany and her army. even better if bran just wargs a dragon, uses it to kill dany then flies it up north and burns all the white walkers and then they all sit around and drink hot cocoa by the fire for the next 19 episodes.