This is a really interesting question Ennie. In my impression, people change as a result of trauma and pain. Personally, my most important lessons in life have been excruciating. These led me to change in my own way in my own time.

I certainly believe others can change though not as a natural or instant result of ageing. I have worked with some colleagues anywhere from 40 to 60 who behaved emotionally around the age of ~ 8-12. Some, not all I've also met a few people in their teens and 20s who were "old souls" and I greatly admired their wisdom and grace.

As for being set in their ways, yes I think as people age they get into their own way. I'm not yet 50 but I'm more set in my ways than I was 10 or 20 years ago. Though I can of course continue to evolve and hope to do so.

In short, I think it depends.