Question About "High Serial Numbers" On Banknotes

I think thats a pretty high serial. I am remembering a post (maybe) by goatie saying he considers the last 1000 serials to be high but I cant quite remember or find the post.

Some people like them. I hold onto the highest serial I can find.
I consider notes with serials in the top 999 serials e.g 999000 & up the high bracket to be exactly that high serials that may be worthwhile holding onto. But it's not something that I believe people really collect.
If it's a First/Last prefix or an error then it's definitely wanted.
I found an average Last Prefix $5 HB06 999855, to me it's a definite keeper.
Otherwise...it might be a yes, it might be a no. I found an exceptional UNC $20 with the serial CA07 999794 which to me is something I'd hold onto.
Depending on the condition of the note will make a lot of difference on who may or may not want it. Personally I wouldn't be buying it because I want to hold the highest note.

Here's some info about part of my high serials in my collection:
I've kept:
Normal Prefixes
$20 CA07 999794 (UNC condition)
$20 JA07 999953 (EF condition, but extremely high serial)
$5 FK06 999905
Special Prefixes
$5 HB06 999855 (F condition, last prefix)
$10 AA06 991433 (UNC, first prefix)
*$5 BO97 999492-3 (UNC, test notes (which are all above 990229))
*$50 JC98 998992 (F condition, last prefix)
$50 AA04 996899 (UNC, first prefix)
* - I purchased, the rest I found in circulation

I've also got a $20 with serial BB06 999819 in average condition...which I'm looking to sell if anyone has any interest in it.
Would it command a $5 premium? Probably not, but someone out there may be interested, depending on what avenues they're looking at taking their note set to.

What am I looking for? A $50 with ? 999998...If I can ever find it.