I have an Ambanja, and he does get a little fired up, but I still can't get him to fully fire up. He could care less about a mirror, and I have two other chams now and he doesn't even get excited about them. For some reason, when my daughter goes to take a photo of him with her iPhone, he tends to get a little excited, and that's the only time. Some chams are easy, some just are very laid back.
I could probably really stress him out to see his true colors, but I just won't do it, maybe it's just me but I like him just the way he is... With spring coming I hope to get him outside more, maybe he'll fire up then..