Many programmers of oldies stations are under the impression that because their music is older, they don't have to worry about adding songs to their library. They have a thousand or so songs rotating over and over and also have thousands of listeners switching stations over and over. In my experience, an oldies audience doesn't want to hear the same songs over and over.
Programmers must continually research and add songs to their library in order to have their stations sounding fresh and to keep listeners tuned in. Edgewater Gold Radio has thousands of songs in our library. The popular oldies continually play but we have thousands of songs that traditional FM radio abandoned years ago that are added to our playlist. These songs trigger listeners to scratch their heads and say "gee I haven't heard that one in years!" That's the listener we're looking for, one who enjoys variety and surprise. We are always researching and adding music to our library. If you listen on any day, you will hear all of the great oldies that you grew up with but will also hear lots of surprises, songs that you haven't heard in years!
My advice to all programmers including internet radio programming, is not to dump a thousand songs into your library and say "forget it." You should always be striving to find more songs and enhance your library which will result in a more interesting and listenable radio station.