Yes, resilient silicone molds deteriorate with use. But hard masters last virtually forever (unless they're acetate originals, in which case permanent copies should have been made), so the tooling "library" remains intact.
If you know what you're doing and are set up to do it, it's less than one full day's work to pull an entire set of new molds from existing masters for one typically simple early annual, Modelhaus-style kit.
A mold is good for anywhere from 20 to 300 casting cycles before it's too degraded to use, depending on a variety of factors like the materials used, the quality of the mold, the complexity of the part, and the care and skill of the person doing the work.
The Modelhaus catalog contained many models scaled directly from factory blueprints, as promos, and as such were very accurate...more accurate than a lot of the shiny new stuff we see today that's been deformed by either the math-challenged, or "creative interpretation" of reality...and some of the printable files available just aren't that great.
I wish I'd invested heavily in Modelhaus kits when the company was still in business, but I procrastinated and lost the opportunity to build my own tooling library at moderate cost.
Scanning, CAD, and 3D printing are wonderful tools to have in the box, but they're not the be-all-end-all answer for everything, any more than a computer is a replacement for a pencil and paper.