Recently, I've run into a bit of a paradoxical situation when I've been writing characters that I've established for quite some time now.
I can best pose it in the question, "How far can character progression go before they simply become, 'out of character'?"
Let's say we have character A, who's known to be a hardass, a stickler for the rules, disciplined, etc.
Over the course of the novel, movie, story, whatever, character A softens up to the people around her. She cracks more jokes, she smiles more, she's even okay with playing hooky from work, all because of her exposure to this new friend group that she's made, or something to that effect.
Look at what you've started with, and what you've ended with. The dynamic is completely different. The way they'd respond to something in the beginning of the story should be a complete 180 from how they would react at the end.
This might be a good thing. It might be bad. But this begs the question, is that progression?
Readers tend to get attached to the way certain characters behave. If you're constantly shifting the morals and the attitudes of a character, it feels...messy. You're not really sure where they stand, or how they're going to respond to something, and it's this ambiguity that bothers certain readers. They expect a character to be a certain way.
Again, an example:
Let's say that character A is asked to skip work to embark on the roadtrip of a lifetime.
Your readers now have different ideas of what the response is. Reader 1 might argue, "Well, she's obviously going to say no, because work is everything to her, and I like that about her. She gets shit done."
Reader 2 might say, "Oh, she'll totally say yes, because she's changed, now. She's happier."
So who's correct? How can both versions of the same characters exist at once?
This sort of idea of progression frightens me a little, because it takes an established character, and does away with the characteristics that make them who they are, in a sense. And if people don't agree with this new version of your character, are you shit out of luck?