I'd like to think the 59 hours are an approximation of the intended usable filmed footage.
By simple logic, it can't be from all the angles available for the two movies.
it must be approximately 200 hours IMO.

I think that by now, many fans are older, and when we know that some people know exactly what's in the archives and what isn't, this secrecy, in my humble opinion, no longer makes sense.
We're all grown-ups now; if there aren't practically any of the legendary shows we all know, you can tell us.
I ...

Is it possible that with Volume 3, this series is over, and there isn't a single more soundboard in Sony/FTD's possession? Not from May or June 1977?
If so, it's clear they'll be in the hands of collectors who don't want to share anything with others, and any chance of hearing it in the future will ...