Should seven wonders of the world be changed often or should be stagnant as itis

There are actually two sets of Seven Wonders....the ancient wonders and the modern wonders. I believe that the Seven Modern Wonders are updated as the times and wonders present themselves. They are mostly architechural wonders more than anything else so that any time a taller building or a higher bridge or a longer bridge or whatever appears on the scene it is usually called one of the wonders of the modern world....whether it stays static at Seven I have no idea.