And Faster is not always better (or safer

).

Do chunks (~25 or less), This stores
everything at the end of the task. A crashed task has no guarantee what the state will be.
fix those issues (
normalize Authors, titles as you go.
Quality check Plugin 
) ) as you find. There will be issues
It took me a long time to document my 900+ Paperbacks into Calibre (some did not have ISBN they were so old

)
(I move the Processed Source folder to an 'Archive' drive,
which also frees up drive space for the Library )