I don’t know why you guys are still arguing. The problem was that once you deplete a key it takes for ever to get it back.
And it has been proven that “no-depleate” does not work. But, timing ANY key (not just your own) should give you some way to upgrade your own key. And that is a sensible solution.
One way is to simply time a key (any key) and it upgrades yours too. Others have suggested using the massive amount of crests were all sitting on to upgrade keys, giving something useful for that currency (other than upgrading gear).
So the issue is solved in my eyes. Its in Blizzards court now to do something about it.