Evolving is definitely a better word than flip-flopping. With flip-flopping, it means you can go one way to another way and back and forth several times. Evolving, I think, means you have changed your mind on the issue after studying it and moving forward with it.

Very rarely do things evolve backwards. There are a couple of examples in the animal kingdom. The Galopago igauna is evolving backward to become a sea creature once again after millions of years on land. The blind cave fish has evolved backward without eyes or pigmentation because of living in complete darkness.

Forward evolution goes on, too. Rabbits around California have begun to develop natural protection from the hemotoxin of the Western Pacific rattlesnake and now the snakes in a certain region of California have actually begun to evolve their venom to be both hemotoxic and neurotoxic.