I was told by Iron Studios directly that they keep the ES open for 4 to 6 weeks but like to keep ES at 999 or less whenever possible with their Legacy Series. That was when I enquired with regards to Wolverine and Weapon X but I'm assuming it is the same here (although I do not know for certain). I find it interesting that we are permitted to order up to two of these ones although that isn't an option for me.
I was going to wait until I saw my Darth Vader in-hand prior to ordering this but since they included both heads, I'm going to order now.