I don't believe he is static, or unchanging. The Fade is not a static or unchanging place, and Spirits are borne of that nature.

... And it's not as if he hasn't changed before. Most Spirits want to know more about life, our world. When I first met him, he was inhabiting the corpse of a Grey Warden. Kristoff. He wanted to learn all he could about Kristoff's life, he cared about his past. His regrets. The things he could do to see justice done for the wrongs done to him in his life.

And he changed in Kirkwall as well.

[ for the worse! ]