I would suggest only "possibly of current interest to an IETF WG".
Too WG-centric, e.g., if draft-jaye-http-trust-state-mgt-01.txt has
expired (it has), and if the HTTP WG has shut down (it has), then no
interested party (using the above suggested definition of "validity")
can exist. Mind, it (and some others) were WG I-Ds at some prior time.
An individual I-D may expire into static dustfullness, or into IRTF
work, or into a non-WG RFC publication. I'm not sure I covered all of
the WG-avoidant alternatives, but WGs aren't the only (or best) metric
of utility, validity, or even humor.
P.S. This document was deleted on March 20, 2000.