> After downloading a site contains thousands of files 
> over a extrem slow connection, there might be 100 
> broken links.  Run the project again may take days.

Try "continue an interrupted mirror" - if the mirror 
ended without much problems (crashes that might have 
cause a data loss) the restart process should be fast.
"Continue an interrupted mirror" will take data in the 
cache first, without checking the "freshness" (darn, 
this might not be good english)