Am I wrong in thinking a selling point of SBCL is that there aren't 'major' releases, and only tweaks and bugfixes, which makes it so reliable and stable?
It certainly is to me. I like knowing that I can run code as long as I want, and not as long as their packagers allow. You can always compile old versions of ruby, python, etc yourself but let's be honest, it's a ball ache. And it'll only get worse as dependencies become more and more outdated.