I think it's an indicator of maturity and wisdom when you are able to revise or reject a position you might have held for a long time. Take Freeman Dyson, for example. He's certainly mature and I find him wise. Over at The Edge, the “annual question”, is:
When thinking changes your mind, that's philosophy.
When God changes your mind, that's faith.
When facts change your mind, that's science.
WHAT HAVE YOU CHANGED YOUR MIND ABOUT? WHY?
and here's the beginning of Dyson's response:
When facts change your mind, that's not always science. It may be history. I changed my mind about an important historical question: did the nuclear bombings of Hiroshima and Nagasaki bring World War Two to an end? Until this year I used to say, perhaps. Now, because of new facts, I say no. This question is important, because the myth of the nuclear bombs bringing the war to an end is widely believed. To demolish this myth may be a useful first step toward ridding the world of nuclear weapons . . .