Yeah, I think keeping an SR Eidolon draw is a bit of a waste. You get a Dark SR Eidolon at the start and clearing the "free quests" in each chapter/region provides with you with more than enough items to trade for an SR summon and weapon of each element(and probably a copy or two for upgrading). Even the beginner bosses can rarely drop SR versions of themselves.

(I've only just started the third region on the DMM version and I'm already sitting on 5 different SR Eidolons.)