I do agree that copyright could last longer than patents, although the current laws are made to grant copyright for many (~6) generations, while patents are for only ~1 (all depends what you call a generation, I estimated at 20-25 years).
And of course this is securing for a limited time to authors and inventors. In other words, it should be limited relative to the life of these authors -- not even life long, let alone long after they're deceased.
The constitution is not a guideline to unlimited powers, but constraints to limited powers. If congress is passing various copyright laws for reasons other than to "promote the progress of science and useful arts" then it would be unconstitutional. In other words passing laws to enhance profits rather than to ensure creator motivation would be unconstitutional, yet that's unambiguously the motivation for nearly all modern copyright law. Nobody is deterred from creating a work because they would only own the rights to it for e.g. 30 years, let alone 110 years.
Well now that we've all agreed(lol) that corporations are now citizens, I'd argue that some do indeed 'live' long after the normal squishy citizen(s) that originally invented/created the thing have died (e.g. IBM).
(Note: I agree with your point, just playing devil's advocate)
No, that is the means of accomplishing the goal. The goal is "to promote the progress of science and useful arts".
Article I Section 8. Clause 8 – Patent and Copyright Clause of the Constitution. [The Congress shall have power] “To promote the progress of science and useful arts, by securing for limited times to authors and inventors the exclusive right to their respective writings and discoveries.”[0]
[0] https://fairuse.stanford.edu/law/us-constitution/