A year after the content was relevant. This is what Bungie is doing with Eververse armor and they should be doing it for weapons after sunsetting or retiring content. There isn't a big leap to move on from weapons since purchasable weapons would have last years power cap and not the new one. This would also mean Destiny would be more inviting. and with more approachable cosmetic items at lowered prices, which them makes other content more approachable. It's just a win-win for everybody involved. Except 3rd party profiteers.