Sorry if this is common sense to some of you.
I always seen them in the free market, but I never purchased any..
 I am not talking about purchasing permanent items from the cash shop, I am referring to those permanent items buy-able with mesos from other people!
1) Is the nx item really permanent first off?
2) Is the nx item that's being sold duped (like say those chaos scrolls from before)?
3) Is there a list of so called "permanent nx items"?
4) If you purchase the nx item from a player, does it expire after some time (meaning you hold on to the item but don't equip the nx item) or "disappear" after equipping the nx item?
5) Anything else you want to add... more information the merrier!
(This is all buying from the free market or through player trading btw)