I have been doing a lot of driving as a part of my job, and so I have been passing some of the time by listening to a radio station that plays oldies.
I have not done this over the years consistently. But I used to live in the same area 20 some years ago and heard the same channel at that time. Now that I am back and listening to it again I can really tell that the oldies format has changed. I knew it would, and remember saying a number of years ago that as time went on, the songs from the 50s would drop out and songs from the 70s and 80s would be in. And that is exactly what has happened.
20 years ago and a little more, of course some of those songs weren't considered oldies, at least in the same sense. Now that I am listening to it again, I like the newer songs but I wish that they would put in some of the oldies from the early 60s and the 50s. Still, those teenybopper songs from the early 60s, along with Herman's Hermit's, the Dave Clark Five, etc., as good as they were and actually still are, they get tedious when they are on heavy rotation. So I am kind of glad those ones are out.
If I am still around in 20 years I will make the same observation!