when to desupport old FreeBSD versions

As Garrett has brought up recently on some changes in gerrit (e.g., 11373
and 11382), we currently have code in the OpenAFS tree which is nominally
conditionalized so as to support FreeBSD releases as old as 5.0, which is
quite ancient at this point.

On the one hand, I don't want to remove support from OpenAFS just after
upstream FreeBSD desupports a release, as I know that sometimes people end
up running things past official EOL, for various reasons.  On the FreeBSD
lists, we sometimes hear anecdotes of companies that have products based
off early snapshots from the 8.x branch, or occasionally even 7.x still.
But on the other hand, those commercial products are probably not using
OpenAFS, and if someone is running an EOL OS they probably already have a
version of OpenAFS that works for them, and don't have interest in
upgrading OpenAFS without upgrading the base OS.

In general, I've been taking that track that I don't mind keeping support
in OpenAFS for old releases of FreeBSD, as long as it does not become a
maintenance burden.  One could argue that 11373 present a case where there
has become a maintenance burden to support 7.x and older.

At this point, I think I'm okay with declaring 7.x and older unsupported,
but since there is an 8.x release still supported I would prefer to keep
around the support for 8.0 along with it, as that's most of the
conditionals anyway.

Does anyone else have thoughts on the matter?

-Ben