I strongly believe in something that will sound blatantly wrong: I believe that a GM should never finish his maps. I’m talking mainly about world maps, but it goes for regional maps as well. Leave some holes in them! By holes I mean certain areas that have never been described. You don’t need to put a big “Dragons dwell here” or “Mystery Region” on them, just leave them blank, for now.
You know what a completed map is? Stagnant. You can’t add anything else. You can’t place that really cool town you thought up or that evil cult’s temple or even the barbarian’s hunting range. Take a quick look at the map of Fletnern. See that spot on the right continent, above the lakes but below the mountains? Yeah - No clue what’s there. Pretty much the same with the area below the lakes. I know it is the transition region between the grasslands to the west and the desert to the east, but I really don’t know what’s there. Same with the northern most section - not a clue. You see most of the campaigns run on/in Fletnern have been on the left continent. There are very few open spots there. Oh I can always fit a small town in here or there, but most of it is considered “designed”. Now having said that, I still have the other three continents that are not on that map that I can always use for wilder adventures.
Without beating a dead horse here, I’m simply suggesting that you don’t detail out every single square mile of your world and determine who the feudal lord is. By leaving some open holes, you leave yourself the ability to expand your world, liven up your ideas, and keep the players entertained.