Ashcroft, when he became AG, set department policy to ensure that this data was retained for no more than 24 hours, which of course set the gungrabbers into a frenzy. God forbid the law should be obeyed when it doesn't further their Nazi agenda. Then when 9-11 occurred, you had the usual suspects, Schumer and Kennedy, demanding that these files be held longer for additional checks, etc., etc. The alarm bells that this set off were from the unspoken admission by this demand that these records were indeed being held for far longer than the legal period. Gee, I'm so surprised.
Ashcroft said no to this, and again the socialists and their leftmedia lackeys had a shitfit, to which Ashcroft said that if the law was changed to legally permit this, then he would do it. Lo and behold, Chuck and Ted had a bill pushed to the floor within days. Current status of that is unknown.
As a computer guy by profession, my not so humble opinion is this: Every damn check that has gone through NICS has been archived. It's too fast, easy and cheap to do. In fact, I would surmise that multiple copies exist spread across several locations. If I was Chucky or Ted, that's what I'd have my lackeys doing. Know thy enemy. So if you've ever been processed by NICS, you are most definitely on the (officially nonexistant) list. Got all that for your book, Trav? $;-)
That's the story to date, as far as I know.