Short answer: Never

FFXIV is not alt friendly, in any way shape or form. Store items are (usually) one per character. Progress is per character. Unlocks are per character. Achievements are per character. If I want to alt up, I lose everything I have achieved, from my main. It's a real disincentive to try out different worlds, different DCs. I don't want to unlock everything again. Above anything else in the game, it's the one thing I wish they would change. Even if its not mog-store stuff. If I have unlocked it in game, let me have it on any character, tied to that service account.