Evolving is sometimes sudden, and sometimes so slow it can hardly be observable. Yet even the Amish are evolving. Their evolving is so slow as to be unobservable because the change is communal, not individualistic. Some small change is allowed by the bishop of a district only if every member of each congregation agrees to change at the same time. At least, that is how I understand it.
In the 1960s, Professor Paul Miller was invited to teach the pastors of the Georgia, South Carolina and Peninsular Florida District of the Lancaster Mennonite Conference. I was their bishop. He knew that we were young pastors, sincere and conscientious, and away from our moorings in Pennsylvania. He told us that it was alright to change our minds. This allowed the pastors and me to evolve and to allow our congregations to evolve.
A polititian like Obama is sometimes accused of flip-flopping when he changes his mind. This is especially true if the change occurs without explanation during a campaign for office. But a polititian with character will publically announce a change of mind by saying I once thought that and now I believe this, and explains the reasons for the change. I think Obama did it the right way.
I tend to trust a polititian who owns and explains his evolution. I tend to distrust a polititian who boasts that he never changes his mind.