Hi,
in the great wide world of BDO it is getting a pain if you have your focused area of activities moved to Grana or Odraxxia where it's not possible to exchange energy to pots and you have to always go through the whole map for this.
Either bring Alustin to the areas like Valencia, Kamasylvia and Odylita - maybe combine with a questline - or simply make this function available through the black spirit.
If you pay attention, Alustin is present everywhere when the story makes him appear and not in other locations.
Since Pearl Abyss seems to take care about consistency towards BDO lore, they need not only to implement an NPC with a turn in option but also justify its presence lore wise or story wise.
While I agree with the convenience about having an energy turnin option at more locations, the previous considerations must be kept in mind.
You could simply make it so it was his assistant or soemthing, he works with other well known alchemists. It could simply be a colleague tat performs the same function if not literally the man himself, but considering he is already in 3 places at once I don't see the problem in making him in 6 or 7.