The Basics of Duration
Copyright duration is simple for works created after January 1, 1978. For works created before that, the rules can be complex, because the works are partly governed by the laws that were in effect at the time of creation. To test your understanding of the copyright duration rules, try the practice exercises on page 670. The answers are here.
In addition to the Eldred litigation, many people are lobbying Congress for the duration of copyright to be cut back, but so far there has been little movement in that direction, arguing that the long term mainly benefits corporate owners and not individual creators. After all, the Copyright Term Extension Act wasn't called the Mickey Mouse Protection Act for nothing.