> the linux-libre project periodically deletes most of its older
> tarballs, even if there are no accidents.

Just FYI that git://linux-libre.fsfla.org/releases.git was created
mainly to solve that problem. Versions are now pretty much permanent.

> It may be useful for users with newer hardware devices, which are
> not yet well supported by the latest stable release, to use an
> arbitrary commit from either Linus' mainline git repository or some
> other subsystem tree.

The cleaning up scripts are version-specific and won't work on an 
"arbitrary commit from Linus's mainline git repository" (i.e., someone
wanting to get today's most recent commit going into 5.9.) The scripts
would fall over and die in such a scenario, or if forced to continue by
using --force the result would be incomplete cleaning. Using the
scripts on a version other than what the precise version that they were
intended for can also cause them to fail in obscure ways, as Vagrant
Cascadian has found out firsthand by running the 5.7 cleaning scripts
on 5.8 (that was determined to be the source of the problems they were
having.) If you look closely at the results of Vagrant Cascadian's
attempt, you'll see there was more than syntax errors: plenty of blobs
were certainly left in. Thus: As said, the clean up scripts can only be
used for the version that they were intended. Use with any other
version invites problems.

> It allows us to update to a new point version (which usually
> includes security fixes) more quickly, before the linux-libre
> project reacts.

Any attempt outrun the Linux-libre project and get updates out sooner
is unwise. While major new kernel releases will definitely require 
updates to the cleanup scripts, even minor patched versions 
occasionally require changes too. Updating to a new version prior to 
the Linux-libre project having had time to review that new version and 
determine if any updates are needed to the scripts risks introducing
freedom problems in the corresponding Guix version.

The moment that the Linux-libre project determines that scripts are
suitable is the moment that the new cleaned-up release is ready to
publish in git and the appropriate tags will then appear in git. The
compressed tarballs come some time later.