I am farming on ultimate currently (on manual though, dont think I can auto them), and I do have some left overs half elixers from last two events.
Judging from your response, the obvious answer to my question is that the shop doesn't refresh and the material requirements for the items just increase as you exchange them?
Also I have some questions about your spreadsheets, but I suppose it's for another day. I can tell you did a lot of good work there, but at my stage of learning, it's kinda hard for me to understand.