The conversion cache building process finished. It ended up taking very close to 1.5 days of processing time. Now I'll be able to sync my iPod with new songs before my weekend trip.
The total was 6317 FLAC files converted, 5588 MP3 files (they were part of the cache building count even though they didn't get converted)
I did bump into an odd bug. After the cache building was done I noticed 26 new MP3 files got added to my library. These "new" files all came from the TEMP directory that MC13 was using for the conversion. That TEMP folder is not in my library or part of my auto-import. The files that got added are temporary mp3 files from the conversion process.
Only 26 temp files out of the 6000-some-odd FLAC files that got processed ended up getting incorrectly added to my library. The temp files no longer exist. If I had "fix broken links" enabled they would likely have been removed from the library automatically, but I don't have "fix broken links" enabled.
An interesting little odd bug. Might indicate a race condition.
Settings:
Auto-import options are all off
Fix broken links: No
Conversion settings:
Encoder MP3 (LAME) VBR Extreme (-V 0 --vbr-new)
Source files FLAC and MP3
Conversion Cache settings:
Cache converted file (via a stack): YES
Stack location: I specified a directory
Cache directory rule: I specified a naming rule ([Album Artist (auto)] - [Album]If(IsEmpty([Disc #],1),,-PadNumber([Disc #],2)))
Then I selected "build cache for selected handheld"