I have no problem with copyrights being a fair bit longer than patents, but I've seen nothing to suggest that 28+28 was insufficient to encourage writers and composers; I object strongly to the notion of incredibly long copyrights being automatic, since it has lead and will continue to lead to the creation of countless copyright orphans--works for which no use is, or ever will be, legally possible beyond the personal enjoyment of people who happen to possess copies. For some works, there may be some people who know that they have, but do not expect there to be enough demand to make it worthwhile to publish that fact. For other works, there is nobody alive in the world today who knows the copyright status.
Prior to the copyright act of 1976, the situation was somewhat manageable: if someone had copyrighted a work at least 28 years ago, and if no registration or renewal was on file, the work was in the public domain. Since published works to be copyrighted had to include the year of publication in a copyright notice, this usually meant anybody interested in a work would be able to know when it entered the public domain.
The 1976 act, however, changed all that. Nowadays, if someone encounters a work and knows only that it was published in or before 1980, that work could still be copyrighted 150 years later even if no further copyright extensions are passed. If the author of that work was born in 1960 and lives to be 100, the copyright will continue until 70 years after his death--2130. To be sure, it would be likely that by 2100 or so one could probably get by with using the work without permission (if one still happened to have a usable copy). But one couldn't be sure that the heirs of the original author or composer wouldn't pop out of the woodwork with a lawsuit. The irony is that the works that under the old rules would have lapsed into the public domain soonest (28 years after publication) may be those which under the new rules never do.
Of course, this is all to promote progress in the sciences and useful arts.