i was quite disappointed with the 15000 gp adventurer upgrade. I half expected them to keep their exp level, but become veterans or something else, since when you have 15000gp to spend on it, you probably have won the game for 10 days or so.
this is really fun but my only issue with the game is that it has no goal, you can't lose nor win, just go for highscores. Perhaps you should give it an ending, a distance goal of some sort