petit c/c que j'ai fait et que je remets à chaque fois vu que personne veut comprendre, et préfère inventer des rumeurs.
unperm means more than 1 item has the same ID
if 2 identical IDs meet on a SERVER , then the 1st ID that entered the server will poof, because the server erased it when the newer one showed up, thinking it is a glitch.
When you temp perm (aka leave a trade) u refresh your whole char, so your ID becomes the newer one, and hence doesn't poof. If the other dude perms too, his won't poof either for the same reason.
There is no time, just meeting on the same server (each server hosts up to 256 games), if u always perm, it will never poof, ever.
If you never enter a game, it will stay on mule for centuries.
The ID can not be changed. Selling/upgrading the item won't change its ID.