After checking my Preference settings, I find that both CGAL Cache and
PolySet Cache sizes are set to 1000000000 (one billion) bytes, and that
number does not accept alteration that increases the size.

Is there some reason for that?

The more I learn, the more I get curious about.

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My settings are changeable but less than yours, ~800M & ~400M.
However I could only change it to 2.1G, I suspect that is unintended,
something like a variable type issue.

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Look like it is a signed int limit 2,147,483,647 (it actually accepts ...648,
but I'd advise against that).
I'll raise an issue on this.

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Issue https://github.com/openscad/openscad/issues/2401  raised.
This could be a hard limit (or 4GB maybe) for 32 bit systems, and may need
fanagling to get more on 64 bit.

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Also check the output of render.

Rendering Polygon Mesh using CGAL...
Geometries in cache: 862
Geometry cache size in bytes: 1612848
CGAL Polyhedrons in cache: 14
CGAL cache size in bytes: 10765200
Total rendering time: 0 hours, 0 minutes, 36 seconds

Note Geometry cache=Polyset cache.

That shows the actual cache used. If the use for expensive models is below
the limit, there is no point increasing it.

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As a concluding note on this series of posts, I also increased the Advanced
Preference setting for  "Turn off rendering"  from 200,000 elements to
20,000,000 elements.

Following the collective recommendations to reduce $fn= settings, I lowered
them to 150 on spheres and 120 on cylinders, then started the render
crunching.

Result was 17 hrs 39 minutes to conclusion.

Did not note balance of computational results.

Are they logged anyplace?

The more I learn, the more I get curious about.

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