For everything before TxP, I keep two copies in my binder unless they're UR or ones that get used a lot (dominants, Lost Souls with good abilities, staples like 2kH, etc.). Afterward, I keep 3 copies, though if I get a fourth of a CoW or RoJ card it usually ends up in the binder until it gets traded. Everything else goes in the box. I have a separate binder for my extra promos - on one hand, I don't want to leave the shinies in the box, but on the other I have enough copies of Chastisement of the Lord.