To the degree the value of the resource is in its novelty (or newness), some songs get used up. They go from being new songs to no-longer-new songs to old songs.
But, not all songs are enjoyed simply because of their novelty.
I was watching that great Les Paul documentary last night, and there’s a whole big section of his career that is pre-1950s, where everyone is doing versions of the same song over and over. And, there’s this pressure to come out with new compositions, but also with new versions of already well-known compositions. The novelty then was certainly as much about “Les Paul and Mary Ford doing their take on the Tiger Rag” than about them writing new composition, if not more.