I just finished off bonemass and am starting to explore the mountain regions. It hasn't gotten old and I actually love the sailing and exploration part of the game.
It would be helpful to have some unique spots or hidden treasures scattered around to make the exploration more rewarding. The vendor was a nice add in this direction, but the game could really use more along those lines.
It is a big world. It would be a shame to only have one unique npc or location to find.