It depends...
My TF Vader stays carded because, to me, that item is only interested carded because it is only interesting with value behind it... Without value, it's a Vader with silver paint all over it... if I wanted that, which is basically worthless, I'd spray paint one.

Carded is all that keeps the piece "interesting" to me, even without wanting to sell it.
For me, a complete silver carded figure set looks interesting... As dull as it is, the complete set is a kind of weird centerpiece to a loose collection.
If someone's uncommon and I happen to have an EXTRA, I'll keep that extra carded, but let's just say for argument's sake I had two Cody's... One's gonna get opened irregardless of how "rare" or valuable he was at any given time. The one I need gets opened, the other sits.
UGH I don't open but then again I don't find them much either... if I do, I buy them to help out friends who've helped me. If I found an UGH Cody and didn't own Cody, I'd offer the UGH to someone for a non-UGH one or some other similar swap to help someone out...
In my collection, the only carded stuff is kept so because it's interesting that way. A loose Lava Vader is dull... A carded Lava Vader w/my ticket from the morning and stuff, that's still sort of dull but it's at least got some "value" to it that makes it a little less dull. Plus it with the other '05 exclusives look good. Those kinds of things NEED some "friends" on the wall carded to make them look good. It's why I think everyone wants to find taped VTSC figures, so they can have a set to open but keep the packaging to hang with the purdy VOTC packaging... Then it looks more interesting.