I am planning to see ZZ Top tonight at a performance in Montalvo in Saratoga, CA. I saw ZZ Top a few years ago and discovered a really amazing thing. It seems that any music artist, no matter who they are eventually gets to that point in their career where whatever they are producing currently doesn't matter anymore. It doesn't matter if the artist puts out his best album of his career, people just like the "oldies". For example, when I saw ZZ Top before, they played a string of their well-known hits ("Legs", "Sharped-Dressed Man", "Tush", etc.) before settling in a mid-section of new songs from their then latest album "XXX". No one seemed to care about these new songs and took it as an opportunity to go for a beer run. Later, ZZ Top said, "We're going to play a few more classic tunes!" which resulted in a huge cheer from the audience. (Admittedly "XXX" wasn't one of their better albums.)
What's interesting is the total opposite happens when it comes to a comedy act. I saw George Carlin once and he did a lot of new material. He closed for the evening by doing his classic "Baseball/Football" analogy. Because many of George's fans were already familiar with this sketch, they started squirming in their seats. Had he been a music act, he would have been cheered for doing his big hits! Weird!