It's inevitable that performers change over time. Those that don't become stale and don't last long (only to regroup later to play the same stuff for a new generation). For some, the change is is not good - they "jump the shark" and the new stuff is not nearly as good as the early. I put Elvis Costello in this boat - never got back to the brilliance of My Aim Is True & This Year's Model. U2 was in it but has come back lately. Other bands, like the Beatles, the change is more of a continual improvement.