(Is there such thing as the Copperbanded Butterfly police?)
I had a medium CBB in my 50g for less than a year, then it moved to a (much) bigger home. It acclimated well, and cleaned out the few dozen aptasia that were there. Actually, it lived in a 33g (12x36 footprint) when it first came home with me - yikes. Call me irresponsible, but it still is my fave fish, and did the job I had hoped it would with the nuisance anemones. The rock is clean to this day- no new aptasia.
I read and heard many reports that were in contrast to my own, and this fish still is reported to have a poor record surviving after capture. However, having J&L get you one is an advantage, from what I've read from different people. They are difficult fish to assess, I guess.