Dunno, but really the only holidays I think are worth investing effort in are New Year's, Halloween, Christmas, Valentine's Day, and Easter. Shame that most of those are Christian-based holidays (I'm not religious at all), but those are probably the holidays with the most "flavor" or substance to do things with. The Talk Like a Pirate Day thing is unique so it's cool, but I really wouldn't mind seeing stuff like St. Patty's Day or Chinese New Year go if it means that work gets put into the game elsewhere.

Five holiday stores and a Revolution/Nexus once per season seems like plenty enough, just my opinion though. I guess there's really nothing else for the basic, non-developer GFX team to be working on though.