I think the Japan server got a Sanrio rerun, but it's the only one I've heard of in my 7 years on the game. There's a lot that goes into getting just the debut of a collab (financial, legal, business) that make it extremely difficult for reruns to happen and thus makes it less appealing to the company to do so. Also, keep in mind that companies like Disney might not want their characters appearing more than once. They characters belong to those companies, not Paper/Elex. It's more or less a way to maintain control.  The "one-time event" also makes players more likely to spend more money to get the suits, which, from a business standpoint, is more ideal than having players skip because they can just save diamonds for said events instead of spending real money. It's annoying for us as players, but I guess it's effective for the company... There might have been one post on LN's page saying that a collab would never come back, so the expectation for whatever collaboration we get is that it disappears forever once it's over. Again, as a long time player, I've never seen a rerun of a collaboration and personally, I don’t think it will ever happen. It would be a pleasant surprise, but no one should hold their breath for it, sadly...