You are correct, it is usually best to stick to the versions in the repositories.
That said, there is currently a problem with the updating mechanism of our repo. I like to keep my browser up to date, so this is what I did:
As root, in a terminal,
mkdir -p firefox/src
chmod +x mozilla-firefox.SlackBuild
at this point, find the version number (3.6.13, at line 14) and change it to 3.6.15
press F2 to save, F10 to exit, then enter command:
it will take a while. When it is done:
You may delete the /root/firefox directory when done. No guarantees. Use at own risk.