Excellent, excellent 12-day game.
I came here because of Dolphin Olympics 2, but I actually had been looking to play an RPG like this for a while.
Some ideas for extending it: if there were a boat that takes you from the outpost island to any of a number of islands on a given day, then you could choose which island to go to each day (and each would have a different distribution of area difficulties / resources). You could extend it to 30 or 60 days.
Maybe have a hill before the mine, and then when players exit the mine to the outpost there's a cut scene with them sliding down the side of the hill.
I found the early game hard and the later game easy, but that's probably because I tried to milk each day pretty hard.
Funny situation: if your commander is heavily wounded, you walk around as a ghost (invisible) each morning until party selection. They tell you he'll be better tomorrow, but he never is.
On my machine (Windows 7) there was about an 18% chance that I'd get a 13-second loading wait before a battle, 18% chance after.