I'm happy with the event and could even make my low level characters farm fast enough, where I can't complain anymore.
But about the egg situation I think it would be the absolute worst decision to remove them after the event ends
What's to gain is less confusion with eggs and recipes from different years and making it easier to sell eggs.
But we'd lose the opportunity to get story token (from red eggs) whenever we need them or when creating a new character and we'd lose the only really consistent way of getting platinum (from plat eggs) without paying after the event is over.
Also with all the options to search in auction I don't feel like it's very difficult to find exactly what you are looking for. Literally all you have to do is search for "2024" and select the rarity of the egg you are looking for.
Maybe a note on old eggs, or in the event information about old eggs not giving any points would help players understand, that they need new eggs for event.