U.S. Patents, at least as they apply to software, seem to have a few inherent flaws that I believe override any theoretical basis for for the 'good' they are supposed to provide.
I'm not convinced that the flaws are really inherent, though I agree that they're definitely there at the moment. And are especially difficult to fix when it comes to software, because it's often harder to nail down exactly what's being patented than it is with physical objects and processes.
That's a separate issue from "how long", though, getting into whether some things should be patentable at all.
Why should there be a difference between author/offspring and a corporation?
Partly for a reason you've already mentioned: that works produced by organizations skew toward the type with a shorter commercial lifespan. Partly because individuals tend to be less able to extract the commercial value quickly, and more likely to need that last few percent of royalties. And partly because individuals are less likely to file suits based on dubious claims of infringement.
I'm using fuzzy language like "tend to" because I recognize that there are exceptions (like a lot of Disney Corp's old cartoons), but I think the ideas I laid out would form a good starting point for debates to arrive at hard and fast rules.
I am interested in this because I routinely deal with organizations that are having trouble with software they use that was purchased decades ago, and the original (and sometimes second and third generation) hardware is failing
Ah, that brings back memories: one of my very first jobs out of school was on a team converting an old 1401-based system to run on 360s. And we faced some of the same technical problems, because some of the old programs couldn't be easily replaced: they were hand-patched object decks for which there was no source or current documentation. We had to do months of parallel runs to make sure that we weren't going to get bitten by terminally-clever programmers who'd exploited obscure quirks in the original hardware that weren't included in the emulator.
My suspicion is that if software copyrights were short enough to only cover extracting most (say > 95%) of the commercial value; then something like project gutenburg would be set up for older software...
I agree, but I see a potential big debate (and, doubtless, years of litigation) over whether, e.g., the CGI for Avatar is "art" or "software".