As adrianh has pointed out, mirroring CPAN is not very hard at all. Here's the two lines from my crontab that do the job just fine:

# Update CPAN mirror at 2am every Sunday
0 2 * * 0 /usr/local/bin/rsync -av --delete cpan.mirror.findityourself
+.com::CPAN /var/apache/htdocs/CPAN/ >> /dev/null 2>&1
[download]

That took me about 10 minutes to set up the very first time, which really isn't half of a day. Extending it to any Unix-ish system (such as Linux, BSD or MacOSX) should take about 5 minutes. That's much less than half of a day. Unless you live on a planet like Mercury. :P