Id keep one copy as collection anyways. Thats just me though. I dont care about CRing units ill never use, like Chizuru who i got 7 times. Bernice, fedora, Iris, Zola etc. though are worth combining until thier perfect no matter the small chance on last CR. The rest goes into RC. But i also used one here and there as AW fodder in the past when i was short on silvers. CCing and AWing a bunch of plats/blacks eats too many silvers sometimes and events where rare.