The point of these limited time events are for players to be surprised. If they know ahead then everyone will farm and nobody will purchase gralat packs. But really all you have to do is spend a couple hours farming to get money. I can make 10k in the grotto by bomb farming in 3-5 hours. So really I don't see any issue here. But what you're suggesting if more time for you so you can take your time getting money.