For wasting one Eidolon inventory slot for ~10 months, you'll get 1/4th of a Raid Eidolon. Or 1/67th of a Kaiser Dragoon.
Is it smart or not is up to you. I'd personally keep it, but... uh... yeah, the gain rather miniscule.
Only Ixion and Phoenix have had second reruns so far, but Yata might get one eventually. I don't think that two LMB Yatas would be a good idea though.