Im throwing my hat into ring here and im going with "Phoeni"
Concerning the Phoenix Tome (that contain the choice of Pheoni - i'm determined with this)
i'm unsure as to the duration of this in the Crafting Recipes. Now I cannot see them getting rid of the Phoenix Tomes in their entirety, I would assume though that they will alter the cost given, as you say, the Twilight Phoenix Event is long gone. They may alter it according to Spire Artefact Rotations!? I don't know... but I definitely can't see them doing away with them.
I am feeding back your comments though concerning the Tomes as always! It will get to whom it needs to go