I hope the story goes on for a bit longer because I'm a fanfiction writer and having the end of the plot announced will stump a lot of plot bunnies and people's acceptance of things since they already know the ending...
KEEP GOING, KISHI!
Like PB said, 200-250 sounds pretty good. Though I must say that knowing the end isn't too bad in some cases aka all those time-traveling fics that have been building up. And since I'm still thinking about writing one, it'd really help because I don't want to make some BS ending that isn't even all that good but at the same time spice it up and make it better.