I think all of Keith's points are spot-on. I'm also not opposed to Archiving as many of these as possible as a general principle, but I, too think checking with the taper would be a very good thing. There is still an ethos among some long-time tapers that physical music trading builds communities and fosters interaction among fans, and that that is more important than getting a show as widely-distributed as quickly as possible (which, of course, isn't quite what you're advocating with these older vines, but it is the more common, more current view for new recordings, it seems). Perhaps the show was offered here as a gift to the Orchard, specifically, and wasn't really intended for the wider world. If the person who shared it initially with that kind of impetus behind it (or whatever the rationale was--doesn't really matter) we ought to at least get their OK if at all possible.
Another reason for this is quality--the idea of Archiving a show from a copy of possibly unknown generation worries me a bit. Sure, the fact that these are vines should cut down on the problems that can creep into this, but if the copy used to prepare the FLAC files is a copy from a friend's copy of a set of mp3s made from the original vine disc that had been scratched three users earlier but not badly enough to complain about it . . . well, you get the idea. I'm not sure that everyone is as concerned (euphemism for anal) with using EAC for digital audio extraction, or burning DAO at slower speeds as some of us

Much better to work from the master or a newly burned copy of the master if at all possible and avoid the avoidable clicks, pops, gaps, etc. that seem to inevitably creep in unless lossless formats are used from the get-go.
Those are my thoughts, anyway. I don't have very many older shows, so I'm of no use for this, but I agree it would be nice to have them available.