This is not really a good comparison because I'm only talking about an AFCAD, which changes more often than a building, terminal, or runway.
We can only be concerned with what we release, of course. Our last AFCAD update for KORD was 1 year ago so, I wouldn't say it changes very often.
We used to keep a separate AFCAD to download on the forum, but it was only during in the early weeks/months after KORD was initially released, because at that time, the AFCAD *was* constantly updated, following user suggestions. We think the one that comes with the scenery now is reasonably stable, and everything else should be a matter of user modifications.
That's why it would make probably more sense to just download the whole installer again, because something else other then the AFCAD might have been updated in the last year.
I am also looking at this from a "user's" point of view rather than a "Scenery Designer's" point of view.
It's exactly from the point of view of an user, which is better to dont even have to *think*, and just download the whole installer on site, to be sure you have the very latest version of everything.
As an user, I really hate when I have to keep a base installer, then keep track of patches or (even worse) separate files, that I have to remember what they did and were to put them. I always prefer to have a single file installation for every game I use, when possible.