``Economic benefit'' a time bomb?

The only benefit confered by a copyright monopoly is that of society receiving (eventually)
another work in the public domain, you say.

That's not actually true. If it was, there would be no reason to have copyright at all for
software. The eventual benefit, another program in the public domain in a hundred years (give
or take a few decades) has essentially zero value. 

But there is one benefit more; copyright stimulates (or is meant to, anyway) the CREATION of
creative works. The theory goes, if we didn't have it, less books would get written, less
software created. Having the book written is beneficial to society -- even before it falls in
the public domain.

We're paying a much too high price though. Does anyone HONESTLY believe that much less
software would get created if copyright was only, say 20 years ? I sure as hell don't. If we
could get the same for a lower price, why then, do we persist in paying the higher price ?
It's just downright silly.