Earlier quoted context omitted.
What do you think is reasonable? 14? 24? 50?
Honestly, I don't mind the idea that you the creator, personally, holds the copyright for life. If I write a song in my 20s that sets the world on fire and I can still live a good life at 80 off the back of it, great. The minute I sell that copyright to someone else (or it's inherited), a time limit begins to apply. Perhaps here you move into the '20 years' or something category.
The screen actors guild has somewhat of a highlander policy, but if I release something Copyright My Name, there's hundreds or thousands of people it could be, including a Pulitzer Prize winning author who will likely predecease me.