While a Dynamic Kernel Module Support (DKMS) slackbuild is available at slackbuilds.org, Slackware is not designed to use DKMS like other distros. Thus, packages that use kernel modules, such as VirtualBox or Nvidia, are not dynamically updated. Would be nice if this was available. Then again, thankfully Pat is not a card-carrying member of the exhausting new-kernel-of-the-week club.

VirtualBox receives regular point release updates, but if you are not affected by any of the bug fixes noted in the change log, you can continue using an older version and avoid needing to rebuild kernel modules. Generally I do not update VirtualBox until I find myself many point releases behind or I notice a serious security patch in the updates. Even then I am not in a hurry because none of my VMs are public facing.