The minting guide say that you should set the policy to expire after certain slot to make sure that nobody can mint more of the same NFT. This kind of makes sense, but then how can you reuse the same policy to mint more of different NFTs?
I saw that most NFT projects share same policy ID, which makes perfect sense, you can verify that NFT really belongs to that same project and isn't forgery, but does it mean these projects didn't set expiry in their policy? Because if they did, how can they keep minting more and more NFTs over time and add them to their collection? What prevents them from adding two identical NFTs?