I don’t know if this game will have a store that will rotate skins in batches within months or weeks or will all new and old skins be a permament addition to the cash shop, but what I do know is that we absolutely need means to see how long sold skins will be still available.
Maybe put a timer under a skin or in the corner of a store page so that no player will regret not buying a skin simply because he was hesitating or putting it off for two long before the store was refreshed.