Everything but two knives is nla

That Busse's business model.  They come out with a knife for a while, sell it for a month or so, then you never see them made again.  Sometimes they make the models again for the Knob Creek gunshow and the Blade show.  Most of the time once they are gone you seldom see them make that same model again. They may make another variant of a model, like a skinny version, fatter version of it, and double cut finish, etc.

To keep collectors buying, spur impulse purchases, and prevent secondary market saturation (value loss).

Side effect is that what would be an awesome knife to really use turns into something you can't replace should you lose it.

I really believe they are outstandingly tough (i've got a few "kin" that I really like.....but when the rubber meets theroad, I take less unobtanium blades with me to the field and my kin stay in my shtf stash.

They do offer new blades (at present) once a week usually on wednesday.
You can sign up for their newsletter to get notified when the new offerings comes out.
I guess the fact that the models they release are limited is part of the appeal to Busse collectors.

Yes, so the limited offerings (usually 1 or 2 models) They go live on Wednesday nights,
then you get the "last call" notification email from Busse after a few days and wont be able to order those models again after that.
(unless you contact them directly and see if they had any cancellations)
There's always the secondary market, tho I would avoid ebay as much as possible.