A couple proposals not originating with the authors are cited:
The first proposal is interesting (80K upon reaching adulthood). However, human nature may foil the plan. We have a tendency to ignore long term gains for short term rewards. I can picture 18 year old guys buying a sports car instead of getting an education, starting a business, or investing in a house for long term stability. Still interesting, though.
The second proposal is something that should be enacted. Currently, families with wealth are able to snowball their wealth to ever larger sums due to a lack of inheritance tax and a low tax on capital gains. The heart of the economy is consumer spending, and the more money that moves from the middle class to the fewer and fewer people at the top, the less money there is in consumer spending. That hurts everyone. I think you already understand why this is a problem, but for those who may not understand the concept . . . A man with 10 million dollars will buy 1 toaster. Split up that 10 million to 100 other people and they will buy 100 toasters. This is probably a little far off from the topic, but still an important economic prinicple (at least according to my limited understanding of economics).
But the expiration dates are ridiculous. Roughly two generations (in addition to the original author) can benefit from the copyright or patent despite having done absolutely nothing to earn that benefit.
Pharmaceutical drugs may serve as a decent model. The patent is 20 years, but exclusivity is shorter, as little as 5 or 7 years. This allows for generic drugs after exclusivity runs out to keep costs down. This FAQ might be of interest to some:
Frequently Asked Questions on Patents and Exclusivity | FDA