That smells like a Google problem. Not with archive.org.
Google has been putting more and more attention to the big commercial sites and less to the obscure, small blogger sites. I notice it when I know I've found the info before (like in years ago) and now it won't crop up, even when I go through every result listed. That's especially apparent when looking for vintage gear. If it's an existing brand, you'll have to wade through pages and pages of shops.
Google is obviously aware and they're working on it. Or so I've been told. It's the use of quotes for exact matches that no longer works reliably. Maybe other stuff too?
Other search engines give even less results. And you can't bookmark everything. At least, I can't. I've even tried a database for my bookmarks, but it always ends up unmanageable in one way or another.
AFAIK, archive.org never deletes stuff. Unless, of course, they are forced to do so by a judge. Which doesn't happen often.