1. They re-stock every 20-60 minutes, I believe.
2. They stay the same for everyone until they become re-stocked, in which case a new hat becomes available.
3. Of course, lol.

I think that they're slightly over-priced. At 3,000 a piece, I can barely even afford two bobble hats, let alone 'collect' them all. Anyway, that's beside the point. It's a nice little update.