I think we should be able to battle Elwood on April first only. I also think the battle record should be wiped clean on April 2nd like it never happened at all. Maybe the loot he drops could be from past Elwood days? Or maybe have the first ten wins appear in random order. Like on your first win you get the screen telling you it was your seventh win, and your second win you get a screen telling you it was your first win, and so on...

I have always wondered how the free gifts from previous years could be circulated again, if not through the Crystal Shop or them being re-used in later years (Since every year seems to have new items). Maybe battling would be a good way, though it depends on his difficulty level. In fact, the difficulty level could keep changing. I don't know if this will happen, though.