To keep or not to keep tarballs

In Gentoo, one normally keeps source tarballs because they are frequently re-used, either for patch updates or for rebuilding packages against upgraded libraries. Is this also the case in Crux? And do the compiled .pkg.tar.gz files need to be kept after the package has been installed? I ask because I do not have a very large partition for my Crux system and I don't want it to get filled up with unnecessary files. -- Hazel Russman <hazel_russman@yahoo.co.uk>