There's really nothing wrong with extracting tarballs wherever you're most comfortable. However, I'd suggest creating a subfolder to extract them to (for instance, I use /home/cerbere/temp/) because some tarballs are poorly created and could extract all of their files directly into your /home/user/ directory. For me, that'd be a real nuisance to clean out.
But getting back to your question, you can delete the folders after installing, but that will make uninstalling them more difficult. So I'll make another suggestion: take a look at
checkinstall. It replaces the 'make install' step when installing from source, and it'll create an RPM (or Slack *.tgz or Debian *.deb) package, as well as entering the correct install/uninstall info into your package manager. This makes uninstalling programs much simpler, so you can delete your source directories with no worries.
BTW, you should enter your distro into your profile here in the forum. That'll make it easier for people to help you. For instance, I don't really know if you have any of the package management sytems that checkinstall works with so . . .
Enjoy!
--- Cerbere
