1. I think the obviousness of an idea might change throughout time. 2. What if one industry is dominated by two companies, in the sense that all the experts are employed by one or the other, then how could they be unbiassed?
There's nothing illegal with being a monopoly. That doesn't mean it isn't wrong. I think in most cases (with exceptions like utilities), not having monopolies leads to a healthier market than having them.
Yes, or changing it from a binary system to a continuum that maxes out at 20 years. Software patent? 5 years. New drug - 20 years. New algorithm (can't patent math of course) 10 years.
