About your discussion of when things become signif and worth preserving,
this is an interesting struggle among cave conservationists. When the Great
Saltpetre Cave (Rockcastle Co, KY -- Ken has been there, with Kathy and
David) was "decommissioned" from showcave status and given over  to a group
of grottoes (Nat'l Speleo. Soc. chapters) for conservation, a firefight soon
arose over exactly what damn date and status they were a gonna conserve it
back to. They had mouldering wooden chairs -- hundreds -- in there, and a
mouldering wooden dance floor and remnants of a stage, because the place had
been the location of the radio show Refro Valley Barn Dance for a long time
(moved out to a great site next to I-75; still wonderful).
        They also had remnants, amazing things, wooden pipes and vats and
tools and diggings, of salpetre mining relating to the  US Civil War and
earlier. And then there was the graffitti.... exactly when does cave
graffitti become bad news, at what date? I guess all agree that spray paint
is definitely over the line. But what about the millions of signatures from
every darn member of the Mullins family in pen, in soot, in pencil, from the
twenties onward, that pepper the walls of this and every other cave in
Rockcastle County?!
        And what do you do about the tons of missing cave formations, when a
more lenient (and very short-sighted) past management allowed visitors to
break off chunks as their own souvenirs? Do you try to restore this glory
using epoxy and moisture-proof seals?
        Anyway I was there the day that the "get rid of all but a sample of
the hellish nasty chairs" subgroup prevailed -- we hauled em out in a jeep
(big cave) and burned them. A few sit in the "display area" of the cave with
shards of the dance floor, next to display cases in the stygian gloom (the
place has a nice set of electric lights that were allowed to stay, because
they emphasize the truly architecturally wonderful glories of this cave)....
all non spray paint graffitti has been kept ("they" say that Dan'l Boone's
signature is in there, after all -- but who has seen it amongst the
Mullinses), and much effort and space is devoted to protecting the salpetre
mining remnants.
        Sounds great but on the other hand, year before last the people
running the protection of this cave allowed Steven Segal to use it for the
"coal mining" portions of "Fire Down Below"....(!!Ken, Kathy and David have
seen this movie). SO things can change strangely.
        No doubt if I got any of this wrong, Deb Bledsoe will correct me
(she is STALSRUS up in Ohio and is involved at Great Saltpetre or let's say
they let her camp there, as she is SUCH a TROUBLEmaker). ANyway, the
discussion over what is signif and worth saving is a great ongoing struggle
in cave conservation.
Hilary in KY