Once you share an idea you should have a chance to be compensated for your work, but it enters the collective unconscious and it becomes part of society.
It's like having a child, you can raise it however you like until a certain point, but then it goes out into the world.
Sure it is for life-- and longer. If a carpenter builds a house, that house is the carpenter's forever. He/she can pass it on to their heirs and those can pass it onto their heirs. The same goes for all physical goods.
And, others have pointed this out, but copyright has nothing to do with ideas. If you want to write your own book with the ideas, go to it.
Once you share an idea you should have a chance to be compensated for your work, but it enters the collective unconscious and it becomes part of society.
It's like having a child, you can raise it however you like until a certain point, but then it goes out into the world.