I'll only give you better efficiency suggestion which is not very related to your question, so you can just skip reading it if you want.

Next event gives thunder/light booster eidolon and other gives wind/water so i dont see why you're in rush. Only main slot eidolon's element matters, others are there for raw stats and their combat skills, so farming for SR eido sounds like a waste, i'd farm materials for elixirs.